Take it from me. Sonic fan since 1991, when the franchise began. It is unbelievably toxic and jealous of other fandoms.
The majority of them are maturing at this point, in the same way that Trekkies had matured and set aside their differences with Star Wars fans, but the nature of the Sonic games means it's full of kids, tweens, and teenagers who are trying to distance themselves from so-called childish things. Thus, these fans are confused and scared of fandoms of seemingly childish things full of adults comfortable with their identities. The majority of Sonic fans, at this point, are content and comfortable too, but there will always be people of those aforementioned demographics coming in and angry and frustrated that not everyone shares their interests and opinions.
SEGA is having financial problems too, having laid off a large part of their employees, which only fuels their anger toward other things further.
They successfully created discord (no pun intended) among the Bronies (
My Little Pony: Friendship Is Magic not only being the highest-profile example of a non-masculine show with a lot of male fans, but also happens to have a main character who's blue and has super speed--there was a lot of fanart of Sonic and Rainbow Dash together, which these Sonic fans
detested, not to mention
Friendship Is Magic writer Dave Polsky becoming the head writer for the
Sonic Boom TV show) and unsuccessfully attempted to goad
Freedom Planet fans into something similar (an indie game franchise that takes a lot of cues from Sonic games but is a lot girlier and cuter than Sonic...while getting much better critical reception than most Sonic games, which made them jealous--and some of its production crew went on to help make
Sonic Mania, which was very well-liked but drove these fans bitterer).
Essentially, there is a small contingent of Sonic fans
who have a deep-seated need for Sonic, as a franchise, to be at the top and revered by everyone. They can't stand something being more popular than Sonic, especially if it's "cute" or "feminine" (or both).