A little goodwill and tolerance goes a long way, bubblyrat, I agree. Clearly you still smart from that treatment, hence the intense feeling betrayed by the capital letters. Nevertheless, I know of very few events where instruments are not welcome, and these are generally well-known and -publicised. They are also far fewer than the tunes-only sessions I know (from where, by the way I have seen even accompanied singers evicted, because they don't fit the ethos of the session, which is "one leads the tune and everyone joins in"). But both those examples are of specialist events.

I found that clubs, generally speaking, will have a preference one way or another, but would be tolerant towards the opposite end of the spectrum too.