People do that, you know; throw other people out, I mean. I think this happens due to the cognitive error known as "mind reading". Person A believes something particular about Person B's motives - usually that Person B really meant to give offense when Person B actually didn't mean that at all. Then Person A writes Person B off.
People, even more than things, have to be restored, renewed, revived, reclaimed, and redeemed; never throw out anyone.
I've seen it a lot. Sad. Unnecessary.
The meditative principles of compassion, impermanence, and considering difficult people to be "precious teachers" will all help.