I find that it's detrimental to mindfulness, both at the time, and it interrupts any cumulative mindfulness that may have been developed recently. I find that mindfulness needs to be a 'habit' and alcohol interrupts this.
That said, I don't find questions like "Can a Buddhist drink alcohol in moderation?" particularly helpful... I think it's more important to understand and address the (generally negative) causal relationship between alcohol consumption and Dhamma practice. Through understanding the relationship, lifestyle decisions can be made intelligently, rather than through resorting to techniques such as blind adherence, proclamations, generalisations, guilt and shame.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)
"To argue with a person who has renounced the use of reason is like administering medicine to the dead" - Thomas Paine