I had very passionate talks online about all 3 categories before I turned 18, and I got a lot of feedback, from older folk I didn't previously know, that I shaped opinions and formed new perspectives - and a lot of the talks sure as shit did the same for me. I cannot say I would have nearly the same current passion that I do for technology, aspects of politics, and philosophy (including that of religion) without such exposures during my adolescent years, and I'm sure you'd be hard-pressed to find others young enough that wouldn't say the same - provided they have an adequate baseline of introspection.
On that note, out of all the examples you could have given for discussion categories that are unbecoming to have with minors, you chose 3 relatively benign ones, lol.