Misconceptions the 'Good Guys' Have

Today I saw a picture that said, "I am gay! I have the constitutional right to life, liberty, and the pursuit of happiness."
Can you guess what's wrong with this statement?
Answer: The 'right to life, liberty, and the pursuit of happiness' is not in the Constitution. It is in the Declaration of Independence, which doesn't actually determine our laws. You have the constitutional right to freedom of religion, freedom of the press, a trial by your peers, and a few other things encoded in what's basically an appendix to the Constitution, the Bill of Rights.
That's not the point.
The point is that if you don't check your facts and know your material cold, why should your opponent take you seriously? How can you argue with an anti-gay-rights person that your rights are being infringed upon if you don't know what your rights are? How can you convince them that you have a point if you say something that's merely in the right spirit, but not factually correct?
To change minds, your arguments have to be airtight. You want to be the one poking holes in their arguments, not the one scrambling while your arguments are falling apart. Granted, you'll probably have more success changing minds by standing up and saying, "I am a gay second class citizen, and this is my story," but when the people on the fence call out to you and say, "Hey. Why should I help you get married?" what are you going to say?
Well, for starters, if you want to do any good, you won't quote the Constitution without having article and paragraph numbers.
For another thing, you won't say something like, "Being gay is entirely genetic." Quoting scientific findings is a lot like quoting legal decisions. You're better off having someone who understands the field putting it in layman's terms. Thankfully, I'm a lot better at deciphering science-speak than legalese. I wrote the paper on this, literally. (You'll get to see it soon.) Here's what we know or think we know:

• If one identical twin is gay, the other twin has a 50/50 shot at also being gay. 
• Identical twins share the same genes. Anything that is entirely genetic will be the same for both of them. Always.
• If a gay man has a gay uncle, they may tend to share a gene on the X chromosome.
• Just because two things tend to happen together, doesn't mean one causes the other. There's a whole bunch of ways things can be linked. For example, you notice that the tree leaves in your neighborhood are turning yellow and falling off. Is the turning yellow what causes them to fall? Is the falling (or preparation for falling) what causes them to turn yellow? Or is something else causing both?
• Fraternal (non-identical) twins are more likely than ordinary siblings to both be gay.
• Some people still claim to have changed sides or chosen their sexuality.

We are not helping our case at all to claim that being gay has been proven to be caused by genes. The best we can do is admit that the whole thing is confusing, complex, and hasn't undergone enough study. Our focus needs to be not on why we are gay, but whether it matters that we are.