I honestly never really picked up too many gay vibes from Ratburn like apparently the rest of the fandom has, but I will admit I definitely see some shades of lesbianism in Francine, and as that AOK Adult Arthur video pointed out, I can totally see her and Muffy getting together as a couple when they're adults.
Otherwise, the Binky speculation is very similar to Mikey from RECESS: they're big softies, appreciate more cultured things in life (for Binky it's ballet, for Mikey it's poetry), so according to our societal mentality, that automatically means they're gay . . . and, I'm not exaggerating that at all; being an artist and a puppeteer who doesn't care too much for sports (and never really had an interest in dating), for years my sister was so certain that I was gay and would try to encourage me to come out of the closet, even though I never was and I never am.