If you call me on a consumer service which explicitly delineates that behavior, why would it be unreasonable for me to see your video before I accept?

Presumably you would know who you're video calling anyhow prior to calling them, so there's not really a meaningful privacy violation...

The only case I can think of is you calling me to expose yourself or something - to that, I'd say that a privacy option where you can make it so you have to add someone before they can video call you would suffice.

If our threat model in 2020 treats "unsolicited dick pics" as rare, and concludes that an "opt-out" setting is acceptable, we clearly haven't listened to what women have been saying for over a decade.

One of the problems with an opt-out setting is that it can become a viable attack vector whenever the application settings reset: "OMG New phone for my 14th birthday" will look like an invitation to some segment of the population.

It's explained here:

http://support.google.com/duo/answer/6376115

Google knows about dick pics.

I don't see anything in that link that addresses dick pics. Is it just the fact that this "feature" only works with contacts?

Yes, which is sufficient. You can call your contacts on skype and then just show them your dick after they pick up... This is neither a Duo problem nor a common complaint (except for in regards to ChatRoulette, where it's also the USP).

I don't see how; the person shown is the one who initiated the call. Unless you're suggesting a flasher or something, but that's no different than any other video chat, except without the victim's reaction being visible (so, still better, actually thinking about it).

I'd rather ignore a call by looking at my screen, seeing a name/number I don't recognize, and swiping it away. This sounds like I'd have to look at my screen and see something I potentially do NOT want to see before I can ignore or swipe away the call. No thanks.

Don't build your worldview around internet rumors.

https://support.google.com/duo/answer/6376115

Don't worry, I haven't.

And limiting it to contacts doesn't solve the problem.

You need to choose your contacts better if you are genuinely concerned by this. They can already call you (and then, presumably, you'll just pick up) and then show you their dick.

Forget seeing random nudity, I don't even want to see a video of my husband's or kids' face on my phone unexpectedly.

Why should my phone be displaying something chosen by someone else unless I explicitly opted to engage with them (in this case by answering a video call)?

Plus, even if I did have contacts with a dick pic sense of humor, I'd much rather see a dick from them after I opt in to the call (so that I make sure I'm in an appropriate setting). Getting one randomly is insane.

Imagine if your husband or wife called you for some phone sex (say you are on a long trip) but you happen to be in the elevator with strangers on the way to your room. Brrring! No thanks.