The thing is you're making a judgement on the suitability of the environment for you to spend a long period of time within,
No, he's making a judgment on the suitability of the
possible environment. By the rationale he's using, nobody can ever go on a picnic outdoors, because it has rained in the past, and might rain in the future. (Oh, nor indoors, if there is a sprinkler system. Best not to risk it being accidentally triggered, right?)
which is being misinterpreted as a judgement upon their character.
Actually, it's being correctly interpreted as the refusal to make judgments on character
based on actual experience, choosing instead to make judgments based on "what could conceivably happen." In other words, it's prejudice against anyone who drinks alcohol, however infrequently, however moderately, and however responsibly.
Everyone has the
right to be prejudiced (and even to act on it, subject to statute in some cases), and IMO society actually couldn't
function without a good deal of prejudice. But this particular prejudice, in this particular context, is
damned peculiar.