Firstly, I'm quoting your post here to avoid the possibility of pulling the original post's location thread off course, which is usually punishable by infractions.
Secondly: To answer your question, it has nothing to do with Eggman, and everything to do with the overall fanbase of the Sonic the Hedgehog franchise. There's just no end to the lunacy they pull off. Combined with weird random perverted artworks on Deviant Art, wanting Sonic as a playable character in nearly anything they can think of, original characters, and going bat **** crazy about wanting more than one Sonic character in Smash, (Which is pretty obvious it's never going to happen unless Nintendo buys SEGA, which I find undesirable) it's mostly the fanbase that makes me ashamed to be a Sonic fan. It's even at the point where I'm starting to wish Sonic weren't even in Smash at all.
Alright let me answer your first part (on my phone so it's hard to type)
I honestly don't know what lewd art on DA has to do with anything, I honestly don't call people who make such "art" actual fans of the series in the first place.
Second, people will make rule34 art of
any series regardless of what it is, people like that shouldn't be lumped in with actual fans of the series whether it be Sonic, Mario, Star Fox ect.
Now about your other part, it honestly sounds like you're generalizing the fanbase, there are plenty Sonic fans who don't act in such a way, visit places like Sonic Retro and you'll understand.
Sonic getting in to Smash was something monumental, Sonic had already appeared in a crossover with Mario so him appearing in Smash was the logical next step. Sonic being a long time rival of Nintendo and being one of the biggest icons in gaming he definitely deserves his spot in Smash whether you think so or not.
Now, I don't know your position about a second Sonic representative, but as for me, I think Optimus Prime getting in is far more likely than Sonic EVER getting another character
That makes no sense, I feel like if Sonic comes back for the 5th Smash that would be enough to warrant atleast a second character. The series is iconic enough and by that time Sonic will be a 3rd time returning veteran which is quite impressive for a third party if you ask me. People already associate Sonic pretty closely with Nintendo anyway and we already have Sonic characters and Mario characters competing in the Mario and Sonic Olympic games so it really wouldn't be a bad thing to have atleast one more character from the series.