I've seen a lot of people say they get nervous and freeze up in an interview, performing far less well than they do on a job. Perhaps for some people this also applies to phone interviews, and perhaps a moderate amount of alcohol might help them avoid freezing up.

To some extent I'm playing devil's advocate, but you did ask for possible circumstances. I suppose in the employer's shoes I'd pretend I hadn't read the Twitter post and go ahead and carry out the interview. If he aces it, great. If he muffs it, I wouldn't make allowances for him being drunk, because he would have demonstrated showing up drunk was lousy judgment on his part.