Is it a legitimate concern to worry some gay group might convert your straight kid?

No, he will never do what he does not want to do, even if the hound him.

If it was possible to shape someone's sexuality no one would be anything but straight 

No.  It's an ignorant paranoid phobia.

You can't convert someone who doesn't like sucking d!ick into it, though you can definitely confuse unexperienced people.

Personally, I would be more concerned about some kid being brainwashed by a group of Young Republicians.   Very scary thought...

Completely ignorant and irrational.

This is completely ridiculous. Lgbt outreach groups exist for those who are lgbt. You can’t convert someone to be lgbt, it’s not a choice. Either you were born that way or you were not. 

Someone could entice a straight guy to experiment. But if he is straight - he just would not enjoy it and stick to women. And if you have a gay kid - you could pressure him into lying and even marrying a straight women to satisfy your vendetta and social norms - but he won’t desire her and he’ll look for guys on the side and most likely divorce her after a few kids once he realizes he cannot live a lie anymore. You sure were being a great parents weren’t you? Now he’s got a divorce, a mortgage, alimony and visitation rights to juggle. If you’d just have accepted him the way he was he’s have found a husband and then either adopted, hired a surrogate or worked something out with a friend if wanted kids.

No, not anymore.

It's much more likely that straight men come to find the joy of man-to-man sexual intimacy all on their own.

And this is why heterosexuality is quickly disappearing in the world.  

Sometimes all it takes is for one of them to suck that kids wiener once to make a convert for life.

No. If people could convert their sexuality, there wouldn't be any gay people because there isn't a gay person alive who didn't first try to be straight in order to avoid all the persecution from butthoIes in society like you.