Simply put, how can one claim to be striving for sobriety (i.e. enlightenment) when one condones the use of intoxicants, claiming a state of non-harmful, moderate intoxication?
The same could be said for watching a sports match, playing a video game, going to the movies, having an orgasm, or listening to music. All of these activities/experiences can interrupt mindfulness, and none of them are especially conducive to the abandonment of craving.
What's so special about the occasional glass of wine or beer?
You'd really have to ask the Buddha, though it seems pretty clear to me... In fact, I think you are missing the point of what I said, which is that you can't argue on the basis of "occasional" or "moderate" since that is not how precepts work. Moderation renders the precept not a precept; one could equally ask, "what's so special about killing or stealing once in a while?" In all truth, probably not that much, but this doesn't take away from the fact that it's pretty darn good, both for your own mental development and for the benefit of other beings, to vow never to kill or steal.
Anyway, those activities you mention are included in the eight precepts, so while there obviously is some sort of distinction between them and alcoholic intoxicants according to the Buddha, bringing them up does nothing to further an argument in favour of moderation in regards to the fifth precept, unless you can show that the third and seventh of the eight precepts are also meant to be taken as guidelines for moderation, which I doubt is possible.
The Buddha's teaching is a specific path meant to lead one to a specific goal, and so there are specific rules to be followed for those following the path. I don't see what the problem is with suggesting that these rules be kept absolutely to the best of one's ability, both as a support for one's own practice, and as an example and support for the mutual observance by others in the community.
Anecdotally, when I first started keeping the five precepts almost eleven years ago, I cried happy tears when I took them, knowing that I was freeing both myself and other beings from suffering by keeping them. I haven't broken them since, to the best of my knowledge and understanding, and I don't think I've suffered any loss as a result (except for my old drinking buddies, I suppose