I used to think the same as your friend, then I bought a little 13.2 mare called Tuppence crazy little thing but would never do anything to hurt you! I have no problems with them to be honest, look at Hattie she is a prime expamle of a nice chestnut mare!
Yes, a horse at College had it, she was still ridden etc, but if you were lined up or stood waiting for someone to jump a round she would fall asleep, a fair few times she also fell over with it! In the end they had to put her down as retiring her was not an option she was such a firery little...
My latest one is the worst I have had, was out hacking at work on a 4yo, there was a donkey coming the other way, my horse gave no warning went straight up and over crushing the top of my leg, resulting in operation, pin, horrible nasty scars and not being able to ride till at least March 2008!!!!