There is.
Nobody has to know you're gay.
Everybody knows you're black the moment you're born.
You can be black and gay an nobody knows about it. Shit most of us didn't know Sherman Hemsley was gay until he died, and some didn't know until I just posted that. Same for a lot of gay folks; nobody knows 'cause it really ain't nobody's business.
Now compare that to being Black. You can't hide it unless you're so light you can somewhat pass for white. No matter what you do, no matter where you go, your Blackness is always on display and people will treat you according to their own prejudices and/or racist attitudes towards you based purely on your color.