defend your statements?
If your "defence" for your actions is "I was an idiot and spoke without checking if I knew what I was talking about and acted without thinking of the consequences", I am going to judge you as an idiot who speaks and acts without thinking, and I am not going to assume that what you are telling me today is any better researched than the previous nonsense you admit you were making up. It's called a reputation.
I "grew up on the internet" when it was full of professionals and academics before facebook and such. If I made a fool of myself I was respectfully mocked and took note to do my research before "acting like an expert" so I would say something more intelligent next time.
I have scrapped my "teenage identity", however if someone did find my old activities I am happy to defend anything I said. The way I said some things might come across as immature, however I can explain that the nature of the interactions and the way the person was treating me lead to an emotional reaction and can generally point out their messages were far more offensive than mine. I then alter the conversation on to the intellectual content of the messages, which was always well reasoned and researched before posting.
Unfortunately the Internet is not the same place as it was then - If whenever you post factual information that someone doesn't like you get bombarded with "you dunt know what ur talkin bout if you fink that, shut up", you aren't ever going to learn the art of constructive conversation, you are just going to learn to "ignore idiots", including "idiots" who have a valid point.