"... suggesting people know the tunes before they play, get to know the music as well as possible and show it the respect it deserves."

If you want all that, then don't run a session, run a rehearsal. Announce tunes beforehand so people can learn them and have the printed music ready so you can expound upon it.

By the way, how do you expect everybody to know every tune when there are 1800 (I think) tunes in O'Neill's Music of Ireland alone?

A session is informal, open to the public and supposed to be fun.

Finally - equating finesse in playing with respect for the music is not logical. People are not showing disrespect just because they are still learning.