Bang on with this. I have known a few people like this, but as you say it's usually much younger people. My own DC were like this between 17 and 21. They were unbearable for this when they were at University, and so were a number of other young people I knew. As you say though, they've normally passed this stage by about 25. I do meet the odd person like this who is a bit older, but it's rare. What is Twinks, like 40-42? I would find her insufferable if she was someone I knew in real life.
All she does is bang on and on about how right-on she is, and how righteous she is, and how she soooo down with the gays and the transfolk. Philip didn't look impressed!. And you're right, she does make it her whole personality. Bit like (some) vegans. As I said, I bet she is a Green Party supporter, and it wouldn't surprise me if she was a vegan!
edited to add,,, SOME vegans. Not all. 
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