I would submit that a lot of the idea that "vegans are obnoxious" comes from defensive projection. I know a decent number of vegans. I've known more at various points in my life. (I'm not one; I don't have the inclination or the discipline if I did.) And I have observed non-vegans transmute "no thanks, I'm a vegan" into a perceived attack and perceived moral superiority when it was not intended waaaay more than I've seen somebody getting a morality-boner over being a vegan.

Your four examples are anecdotal, much like mine, but we also see this sort of defensiveness around other topics where the conventional morality has some problems that conventional folks don't conventionally want to grapple with. I like Ian Danskin's work in general, but the way he looks at this in particular has resonated with me: https://www.youtube.com/watch?v=ExEHuNrC8yU

I think has more to do with the fact that any sort of vocal veganism is considered obnoxious in the US. So yeah, anyone who tells you they're vegan will be labeled as obnoxious.

Yeah if only we could figure out how it got associated with obnoxious people in the first place.

I guess, sure, you can chalk it up to "those annoying people" and just be done.

Or you can look at the way that many Americans (for the purposes of this discussion; I am one, and I don't have sufficient insight into other folks) react to anybody suggesting anything is wrong with the status quo. America has not a conservative problem but a reactionary one, even outside of what is generally considered "political". This is part of the American hypocrisy about "leaving politics out of it"; most folks with a political education understand that life among other people is inherently and inescapably political, but it's only those who want to change things who are accused of "bringing politics into it", while the nature of the status quo is taken as implicitly apolitical.

To this end, I often see people react as if somebody else being a vegan is translated into being an implicit threat to a non-vegan's way of life. Similarly, you see this with those "normal people" finding gay marriage to be a threat to the "sanctity of marriage" or whatever (gay people are gonna make heterosexual marriages worse, are they?) and you see it with the completely bent way that Americans have and historically have reacted to the notion of somebody being "a feminist"--well before the internet's even more bent notion of some kind of "SJW menace" arose. I tend to think that that has transmuted into this reputation as much as any "bad apple"/obnoxious jerk has been, if not more.

Only thing you can do about that, IMO, is to not be reactionary and not make arguments that seem in the slightest threatening to people. Taking the marriage example, if someone brings up "the sanctity of marriage", instead of just being against that idea, I point out that I agree marriage is sacred and as such I don't want it being subject to definitions in a vote, or having sacred religious ceremonies attached to tax incentives. I think I've changed more than a few peoples minds with that one. People are irrationally reactionary, I agree, but the best response is to not give them so much to react to.

As a white, straight, cisgender male, I don't have to give anybody much to react to. When I go at somebody because they're being horrible, it's a choice (and one borne of a certain kind of community; as a white, straight, cisgender male, it's really hard for those reactionaries to bite me).

Were I black or gay or trans or a woman and American reactionaries are threatened by me for existing, it is not a choice. When your existence is a political question and a political threat, it is not so easy to simply "take it easy".

>Were I black or gay or trans or a woman and American reactionaries are threatened by me for existing, it is not a choice.

Everyone else is at risk, but white men are some homogeneous group that bands together to hold everyone else back. Do I have that right?

I don't think I explained my last point well. Someone, and it was probably conservatives that started it, turned the gay marriage debate into very much a your-definition-versus-my-definition debate. Very few people I think would actually support eliminating the existence of gay people. But a lot of people would be called to action if they feel that the government is going to define something that is part of their religion differently from their religion. I think "if you don't like gay marriage, don't get a gay marriage" is a great argument. But then people who don't want to bake a wedding cake for a gay marriage get taken to court and lose. If you can understand how people wanting to make gay marriage illegal makes gay people feel like their existence is threatened, it's not much of a leap to see how people in the Bible belt look at that sequence of events as a similar threat. So stop the adversarial nature entirely. The government doesn't get to define your peaceful, consensual relationships. End of story. If I want to not bake a wedding cake, and if they gay community wants to take their business elsewhere? That's the respective individual's business. If I want my next of kin to be a man, or a woman, or neither, or multiple people, that's my business. No one's church stops being considered a church because of beliefs regarding a protected class. No one's getting tax breaks for their relationships that other people don't on the basis of gender. Who can feel threatened?

edit: I'm trying to get away from arguing with anecdotes, but let me share a more extreme illustration of how a Christian might also feel "threatened" since you clearly already empathize with the gay community and why they feel threatened. A while ago the library in the next town over hosted a "drag queen story hour". They explicitly advertized this as being an event for children ages 2-8, where kids could come and read with a drag queen. The library said this was to promote diversity and understanding. Obviously the bible thumpers lost their minds, and the library then pulled one of the performers from the event, citing concerns about that performer being bullied. I googled that performer's name as part of trying to figure out what this was all about. The first thing I found was a video of that person, outside, in public, in a major city, masturbating with a toothbrush. The second thing I found was that person in lingerie kneeling before a Christian statue with what I assume to be simulated ejaculate on their face. This person, using the same stage name, was being promoted by the local government for a children's event. And objections about the appropriateness were labelled as bullying. If you're an otherwise peaceful, church-going person who has not previously been much of a party to any LGBT discussions, do you see why these people might feel like there's a threat to their way of life as well? And why they feel disrespected? There's not a lot of openly gay people in this town. This, and media, are all the exposure any of them gets to alternative sexual lifestyles. I don't know how you come back from something like to a reasonable discussion about the real bullying that happens.

Isn't it odd?

We have these ethical giants among us, screaming "bullshit" and making assumptions about the rest of us based on their personal values.