There's a big difference between scrutinizing code and putting down the programmer. It sounds like the people you showed your code to didn't know the difference.
Scrutinizing your code should be talking about the code, and nothing else. Emphatically not about you as a person. It should be about where the code is good and bad, and how that's being measured. The person scrutinizing your code should be able to explain their opinions, based only on the code.
It's really tough to separate critique of code from critique of the person who wrote the code.
Good luck.
GitHub is fine. I've yet to see a troll problem there.
Try contributing to a GitHub project you like, run by civil people (check closed issues and PRs to see what people are like). Accept critique and grow.
Of course the fastest way is with a mentor, but they're hard to come by.
You'll run into bad reviewers. A lot of people use code review as an excuse to feel better about themselves. If this is for fun (and not in a professional setting), try asking some people you trust or believe will be fair to review your code for a while before exposing it to the public.
Good code reviews are learning opportunities and sanity checks. Bad code reviews are gate keeping exercises and personal attacks.
Also there very few perfect coders. Just about every one can benefit from a little code review.
I remember reading the google founders where considered poor programmer but they sure figured out how to change the world. It's not how you code but what you do with it.
Just do your thing. You will be a better programmer than some and not as good as others. Focus on making the best use of your talents and not the talent of others.
It's not great to use public forms though. Revision control systems and hosts like GitHub are designed to facilitate a professional scrutinous environment