When Xander finished flailing, he probably would've sputtered that that was the point; the idea that he was involved in any way with Andrew-flirtage is as ridiculous as the idea that Vic and Pippi were up to OMGDIRTY! when they were smart enough to off together to avoid Andrew.

And then he'd point out that even if there was flirting it was all on Andrew's part and how does some dude he doesn't remember from high school having a crush on him translate to him being gay, OMG? Dude, he likes girls, seriously! Even if they're mean and evil!

And then he would go back to reorganizing his closet and suffering from Joss Whedon's complete inability to allow his characters to pronounce the word 'bisexuality' Willow we're looking at YOU really hard.