Re: serving alcohol
Intoxicants were forbidden in the Qur'an through several separate verses revealed at different times over a period of years. At first, it was forbidden for Muslims to attend to prayers while intoxicated (4:43). Then a later verse was revealed which said that alcohol contains some good and some evil, but the evil is greater than the good (2:219). This was the next step in turning people away from consumption of it. Finally, "intoxicants and games of chance" were called "abominations of Satan's handiwork," intended to turn people away from God and forget about prayer, and Muslims were ordered to abstain (5:90-91). (Note - the Qur'an is not arranged chronologically, so later verses of the book were not necessarily revealed after earlier verses.)
If Allah has called it "Um-ul-Khubais" (Mother of all evils) as it leads to a lot of other sins, then it is better for a Muslim to abstain from it. Even if Allah (s.w.t) didn't mention it haraam, it is enough of warning for us WHEN HE (THE ALMIGHTY) MENTIONS IT TO BE BAD.
If my boss doesn't specifically calls anything unhallowed but tells me it is bad, then out of respect I shouldn't do that work..