Sound advice. It's easy to collect some downvotes by posting about anything people feel passionate about -- there's always going to be somebody who downvotes out of dislike for your opinion. Also, I believe criticizing certain national governments attracts an outsized share of downvotes / flags.
These exist, but I'm not sure it's as cut and dry as that. Sometimes arguments you've seen, or made yourself, that were open ended and/or asking for discussion get downvoted, but sometimes it's just a week later and they don't. I think a lot of it has to do with the context people see it in, their own state of mind, and whether someone happened to take up reasoned discussion on the topic before downvotes started accumulating.
Put another way, I think there's a lot of people that see someone looking to talk about a topic and immediately assume they are looking for an opening to express their outside views rather than explore the topic (which is not fair to assume, IMO). Seeing people discuss that topic rationally stalls or negates that knee-jerk reaction.
In other words, it's a crap shoot (but there are strategies for broaching these subjects that work better than others).
On the other hand, in general I don’t care about the occasional wave of downvotes. They’re fake internet points—-no reason to tie your HN karma to any measure of self worth. Literally anything can and will get down-votes here. Hell, just yesterday I wrote a long-ish story about some ethical issues I encountered as an engineer. No arguments or judgment passing or controversial stands—just a “here’s a little snippet of my career” and it got a couple downvotes. No need to sweat them. The advice to not complain in-thread about downvotes and not attack/question your downvoters is good advice. It’s pointless because everything, including uncontroversial comments, high quality comments, correct, incorrect—-they all get a few downs.