As well as the series Saturday AM, as also the comics from the US-american Archie-Comic series, but unfortunately especially hard is the point on Sally.
If you take a look on the fandom of Sonic, you unfortunately have to realize that the fanbase is extremely fragmented.
Some people like only the videogames (most of the Sonicfans do it), accordingly those kind of fans mostly also prefer Sonic and Amy together, (by the way: some people only like Sonic in 2D and some only in 3D), then there are some people which are only interested in Cosplay, on the other hand there are also people which are committed only to draw and paint stuff of Sonic and co., whereby there are also people who only love the anime Sonic X and/or every series of Sonic in general and/or the comics; additionally there are also fans who are only loving separated, scattered characters; but furthermore it should be also mentioned that there are also existing fans which are loving everything of Sonic, it doesn't matter what it is.
Those are only a few of a lot of more examples.
Some people are suggesting, that the hatred comes from the reason, because Sally have just not much appearances in the videogames and she would be not a permanent feature of the division of Sonic, or just because she is offended from a lot of haters as "naked" ect..
Reasons back and forth, the hatred is really stupid, useless and naff!
Nobody would like to see so much extremely hate towards her/his favorite character!
Some of us Sallyfans wish very much, that Sally would get new appearances in the videogames in the future.
The opinions are going different ways, how everyone can see.