this is my sideblog so i can't send you an ask but what i did/do is curate my own space in fandoms. in my main fandom (not tmnt), i have a group of friends/a circle for my otp and favourite characters and i don't go out of my way to interact with people i'm not familar with unless i see we share interests and i feel comfortable. if strangers want to chat to me or whatever, i'm cool with it and would only block if they act weird or hostile, or if they post stuff that makes me uncomfortable. i tend to draw in people with my fanfiction (again, not tmnt, at least not these days).
i just want to make a quick mention here that i am not a pro-shipper. i dislike incest ships on principle. i do not think leorai is incest so my take here is based on having this stance. if you think it's incest and like it... this won't really apply to you lmao.
you are not going to convince everyone that leorai isn't incest, even though i really don't think it is. it's a sad fact. you can say 1000s of times that they're not blood-related, that they did not grow up together and they do not consider each other siblings and a bunch of other stuff, and there will be still people who go 'b-b-but splinter is both their dads! even though their relationships/dynamics with him are significanlty different' or whatever. at the end of the day, leorai is iffy and i get why some people will be uncomfortable with it. people are free to have their own headcanons on the leorai dynamic and if they want to pretend or imagine they're siblings, whatever, but their projections don't make it true or mean i have to agree with it. and i'm sure they think the same about me in inverse.
i've not been harassed for shipping leorai but i've noticed people in the fandom block me which i honestly don't care about as they're not people i'd want to talk to anyway. i love tmnt but i'm not really in the fandom, if that makes sense. i usually enjoy it by myself.
i don't think shipping leorai is a particular indicator or any moral judgement. i've been called homophobic for shipping a different m/f ship even though i'm a lesbian. i've been told i support abuse, to kill myself, i've been called slurs and harassed for shipping something (not leorai) which imo was a pretty harmless ship that the fandom convinced itself was bad because the fandom is full of kids and people with no literary skills or understanding of how relationships work.
now for a little story. when i was 15, i joined the tmnt fandom and hung out on deviantart. a big pro-tcest and anti-tcest movement went down. lots of arguing and fighting. it was chronicled on a drama lolcow site until the people running it deleted it because they thought it was incredibly stupid. i ended up losing practically all my friends at the time because the admin of the anti-tcest group was extremely homophobic so while i hated tcest too we fell out because i'm not homophobic. and obviously i don't like tcest so had no friends there lol.
this is rambly and i apologise but yeah basically you need to shut out the noise and do your own thing. :-)
EDIT: Also lbr they were not intended to be siblings like what is this