In reply to JimHolmes69:
> But he has dropped some people!
If you think someone is unsafe, there is no option but to take them aside and have a quiet word. Best to do this in a non-humiliating way, to allow them the metaphorical "climbing down gracefully" option.
There are 2 kinds of unsafe however :
1. the "someone is doing something wrong" type - point it out to them, give your reasons why you think it is wrong and any authoritative references if you can find them, and how they can remedy it.
2. the "this person is a liability, always will be and is an accident looking to happen" - nothing to be done but to take them aside and say "sorry, I think you are not suited to this sport and don't have a suitable mindset or awareness, so I think you should stop it/confine to indoor climbing, in any case I/we will never climb with you again"
I have had both types, both very enthusiastic. The "doing something wrong, had learnt too quickly, had physical climbing ability but not enough background, but had the nous to remedy their errors" managed to terrify me on a trip away, I had decided to have a word about his specific faults as soon as I saw him next. Unfortunately in the meanwhile he had gone away with somebody else. During that trip, he decked seriously and was crippled for life. So my little talk intention was too late.
The other also thoroughly frightened me, on a Scottish Winter weekend. As I knew all the ice-climbers he would know, I spoke to all of them separately and made sure none of them would climb in Winter with him. I was still very worried by his deadly combination of extreme enthusiasm coupled with what seemed like a total and insuperable lack of awareness of the mountain situation, but thought that he would be safe enough in the more controlled atmosphere of Summer rock climbing.
He tripped and fell when descending from a popular Welsh crag and was killed instantly. In the discussions afterwards, it became clear that everyone who had climbed with him had had serious disquiets, but no-one had added them all together.
You have to say your piece, for preference in private and at a quiet time. Might be worth writing down what you want to say. If he ignores it or reacts aggressively, just say, well I and XXX will never climb with you again, because of what I just said. It doesn't matter if you are right or wrong in your criticism, as this is your decision to not climb with him, but it is much better to be sure of your facts.
With regard to relationships or attitudes, that is another matter. As always there is no right or wrong answer, just a point where you decide you can't be comfortable with him around.