Astolfo has a huge penis and is canonically a top/switch (Chevalier d'Eon is his bitch, but he plays games with people like his master./Sieg and can flip flop). But he isn't brown, swole (though the manga has him pretty /fit/), nor derogatory towards the sexuality or feelings of others. Nor does he give a fuck what people look like. So yeah, everything about that pic is yikes.
Anyone who actually bothers to know anything about the character knows this: Astolfo will fuck anyone, be they cis or not, straight, gay, or what have you. So long as he likes you, he will indulge. So yeah, "shut the fuck cishet" brown masculine Astolfo is some creepy twitter tranny trying to co-opt the character to their agenda, and can fuck off.