The thing about working in the service industry is that these people are generally hired because they are experienced and good. There are usually two ways I see someone being a troutty server: 1) they are having an off day, 2) they are new and don't know what the smurf they're doing but are trying.

Either way, to deny them a tip that is typically expected just because they didn't provide top-tier service-to-the-Queen waiting on you is just plain kindof cruel. It is a part of American culture to tip. I guess I usually look at it that someone else is going to need four or so bucks more than I am, and it's probably going to ruin their day if I skip out on that.

Be nice and leave tips!