YouTube is not necessarily known for being the kindest place on the internet. Many very popular YouTubers have spoken out about the hateful comments and online bullying they've experienced. Thankfully for me, I've been spared from any of that. I don't know if it's because, as sewists, we are generally a kind community or if my channel just isn't big enough, yet.
I have only received a handful of negative, hateful comments. Mostly people just being really judgy. And, each time that's happened a viewer has come to my defense. More than anything, people will comment negative things about the product or pattern I'm reviewing. It's hardly ever directed specifically at me.
Maybe it's my age or the fact that I've been numbed to this sort of thing over the years on social media, but no negative comment really gets to me. I know that the truly hateful commenters are just angry and hurting and I'm able to compartmentalize that and let it go.
But, if you have a thin skin and would be easily effected by people's opinions of you or your work, you can always turn YouTube comments off. It's not the best way to build a community around your channel, but it will allow you to ease into things a little and block the negativity until you're more comfortable.