I'm just going to go on the fact that:
1) in this thread you (or maybe someone else) has talked about pecking order in male groups and how short men are usually on the bottom or near the bottom of this pecking order.
2) you feel excluded because you are the shortest out of the men around.
3) guys like to tease each other and pick on those who are "lower in the pecking order"

Your conclusion about not being included because you are short doesn't match up. If it was true, then that group of men would be trying to include you because they would view you as suitable short and thus at the bottom of their pecking order. You would be an easy-in because no one wants to be the most-picked-on.

That makes me think that their reasons to not including you has NOTHING to do with your height, and it would have to do with something else.

Do they know what things you are interested in? Have you ever talked with them about things that are a common interest? If you haven't... then they probably think you aren't interested in any of the things that they do, and don't want to invite you out because they don't think you would enjoy yourself.

Your example of that group of people, while sad and frustrating when it happens, does demonstrate a lack of understanding on your part. Clearly they were discussing something that likely they didn't want to discuss in front of a stranger - maybe something about one of their personal lives, who knows. You interupted, and while that's ok, you didn't take the social hint of the conversation totally stopping. Like, I'm not saying that it was cool of them to not find a way to include you... but still.

I would stop worrying about your height and start trying to figure out what the actual reason is. I could understand more if you were complaining that women were never interested in you due to your height.. .cause taht would suck... I've just never once heard or seen guys exclude another guy because he was short. Not saying that it doesn't happen... but you also aren't significantly short.