i don't have any strong feelings about eridan, he's fine enough as a character, but i feel like people pointing out at the contradictions in his actions and taking that to mean "he doesn't actually believe all that racist stuff" are missing the forest for the trees.

yes, eridan isn't entirely ideologically consistent - but so are most trolls, and hey, even a lot of people irl. especially when it comes to bigotry and right wing ideology, it's irrational and nonsensical and nonetheless sincere. the first troll we're introduced to is karkat, who literally wants to be the number one empire bootlicker despite being someone who the empire would love to kill. even eridan's whole "seadweller supremacist despite hating living in the sea" thing seems to be a somewhat deliberate jab at all the not uncommon cases of non-white white supremacists. a lot of people who hold fascist views believe themselves to be the exception, that if they just align themselves with fascism hard enough they'll prove themselves to be the mythical "good one".

and, honestly, the fact that he's "friends" (term used loosely because they all hate him lol) with lower castes is not even because he values them as people. one of his defining traits is his neediness for romance, and most interactions he has with the other trolls are opportunistic along this thread - he attempts flirting with basically everyone, and again i don't think it's because he values them as people. we briefly see what it's like to be in a relationship with eridan from feferi's perspective, and from her account it's basically just taking care of his neediness at the expense of your own feelings. it's nothing like a balanced relationship, and this fits in line with eridan constantly soliciting (particularly black rom) flirtations, despite the outright rejections.

homestuck touches on the fetishization as an extent of racism with its other prominent racist character - equius, and the way his relationship with aradia is definitely like, a weird fetish thing of getting off on authority and the subversion of authority. and i feel like a lot of eridan's solicitations follow along a similar line, albeit more subtly - his relationship with sollux is definitely colored by the fact that sollux "stole his girl", and eridan's response to this is to attempt to hate fuck him. if that's not opportunistic, idk what is. hell, his ideal relationship configuration in the beginning of the comic is having a red rom top of the ladder girlfriend, and a black rom non-seadweller but still highblood girlfriend. his racism and incel tendencies mix with the fact that hatred is a form of romance in his culture, so he tries to pull anyone he can into a relationship with him.

i think ultimately this is what makes eridan an interesting character, it's pulling at his ideology and his actions and seeing how he justifies the contradictions for himself, what motivates his actions and how that reconciles with what he states to believe. making up a "this is why eridan is secretly not racist" theory just makes him more boring, imo, especially since most of act 5's bread and butter is several trolls examining the contradictions in their beliefs and identities, and seeing the (often disastrous) consequences these contradictions lead to.