How so?
I think the version of that for our generation is the person who says "Gosh let's not talk politics" about obviously political things when doing so is clearly just to shield preferred targets from criticism. Of course it's not always that, and you can never prove it in any particular instance, which is why it's such convenient phrasing. But it gets eye-rolls for a reason.
Based on your misunderstandings of US defamation laws, and the fact that you jumped to stabbing over shooting, it sounds like you've been steeping too much in eurotrash defamation rules. Here in America, truth and opinion are both perfect defenses against defamation lawsuits. My comment consisted only of true facts (the man donated to support prop 8), and the opinions that follow from those facts (the man is a scumbag). You can only sue someone for lying about you, and for public figures like a CEO, you need to prove they were lying on purpose.
If your political views are "lets abuse a minority because I find them weird", those aren't merely political views.
How that analogy compares to being against same-sex marriage is going to vary from person to person, but times change, as does what is considered just political views vs a civil rights issue.
Only in the US, South Africa and Rhodesia.
Same sex marriage did not exist anywhere in the world until very recently, and still does not exist in most of the world.
Well, I guess that too has its caveats. Hilary Clinton and Barack Obama were both vocally against same-sex marriage during run up to the 2008 election, I believe roughly the same time that the Prop 8 fight was happening. They didn't switch sides until public opinion started swaying in favor of it and I've never seen anyone hold their feet to the fire or call them "absolute scumbags" over it. Well, no one that wasn't already calling them that at least.
I am not opposed to any of the things your examples of progress, just felt the need to mention that your argument is begging the question.