Here's what I ended up having to do. First of all, just blocking the number of the original group texter (the inconsiderate a$$ who put me in this position) won't do anything to block all of the responses from each person in the group. See the problem now?
So I had to jot down all the phone numbers of each person in the group, then went to the messaging app (not the actual group text, just the part where it shows all your latest text conversations). Click the menu button, then settings, scroll all the way to the bottom. Third from the bottom is "Add to spam numbers". From there, you will be able to add each and every one of the numbers included in that group text.
This isn't going to be ideal for everyone, because obviously you'll no longer be able to receive texts from the other individuals in the group. It works for me because I'm not friends with anyone in that group. But if I was, I just wouldn't block those numbers(s) and would have to put up with their annoying responses to a group text that I have no business being in. In this case, it's my old softball team. I'm not interested in playing anymore, but the coach doesn't seem to be interested in not including me in the group texts!