Alcohol is not a trip killer. It can take the edge off, but it can also produce the opposite in people. It makes the trip more volatile and emotional.
It's not dangerous per se, but you don't feel the alcohol much which can lead to people drinking too much.
I'm an alchy, so I typically drank a lot whenever I tripped. It definitely muddies the water, but in other aspects goes quite well with certain drugs like LSD.
I tend to get kinda sedated on shrooms, so I typically lay down for most of it and only drink when coming down.