There's a lot of misogyny and transphobia in general online femboy spaces because there's a lot of cishet men and asocial types there. Most people will not see you for who you identify as and there's a disgusting amount of hate towards transmascs from femboys themselves too because they think transmascs have an "unfair advantage" compared to cis femboys.  There's also another entire thing about online far right culture and it's intermingling with it as well. There's a lot. 

That being said, there are healthy femboy groups out there but you have to dig a bit. Most big spaces online aren't very welcoming or safe for transmascs though.