WNBA's Mistie Bass -- Rips Gilbert's Sexist Rant ... 'I'm Not Ugly'

"I think what he said was sexist and I'm not ugly. I know that and I don't need him to tell me I'm not." -- WNBA champ Mistie Bass on Gilbert Arenas.

This video is awesome ... the Phoenix Mercury star joined "TMZ Sports" (tonight on FS1 at 9:30 PM PT, 12:30 AM ET) ... and sounded off about Gilbert's "sexist" tirade about female basketball players.

Bass is great -- and spells out her issues with the ex-NBA star ... telling him he should RESPECT female athletes instead of objectifying them.