A few points:
The 2A argument is a bit different. Personally, I can see both sides. Some of that may be my American (and southern) upbringing and environment, but to me, I can see both sides. One side argues that society is safer with guns because police can't be there in 5 seconds and you can protect yourself with one, the other side argues that a proliferation of guns is what makes society unsafe and that adding more guns to the mix just makes it worse. Both are valid points. Both sides, from what I've seen, have made valid points at times, and stupid points at others. This to me makes me think that the whole issue is far too complex for a simple binary choice, and also that our society's problems are a lot more complex than whether people have easy access to guns or not. I could go on and on about this subject, but at the very core, both sides have the exact same goal: a safe society for everyone. Neither side wants a society plagued by crime and violence, they just disagree on whether having legal access to guns helps or hurts this.
Gay rights is rather different. At its core, it's about equality: should homosexuals have the same rights as everyone else? Should they be allowed to live their lives peaceably, or should they live in fear and hide their orientation for fear of being ridiculed, harmed, or murdered? I honestly don't see how it's any different than civil rights for minority races. The only justification for oppressing gays is purely religious, and not based on anything rational at all. People hate them because they're different, and that's it.
That said, as for various smart people you listed, everyone does stupid stuff from time to time. I like to believe that we should *try* to be smart in our actions and beliefs, rather than being content to be dumb, but even the smartest of us do stupid things sometimes. Also, not everyone is smart in every subject. Being good at math for instance doesn't mean you've seriously thought much about ethics.