If a guy you met on a dating site keeps buying you liquor when you go on a date with him what would you think?

It depends. Did you meet for your date at a bar or club? Kind of difficult to buy anything else at this kind of venue.

If this was for a church picnic, I would consider that he might be an alcoholic, trying to see if you are, or a wanna be rapist trying to soften you up with alcohol.