If I read the first post correctly (and I did cause I don't make mistrakes er make that mistakes ) , the guy is not dumping his best friend He is just not going fishing with him anymore . Its Nothing to lose a friend over .
Fish are merciless predators who make their living killing and eating thousands of tiny creatures and I have no qualms about killing one but I seldom do . I fish barbless and practice C&R . If I hook one in the gills , I keep it . I keep the odd one to eat when I am camping and cooking over the fire , its part of the outdoors experience that I enjoy .
I used to be an avid hunter , but no longer find sport in killing animals .
If asked to participate in a hunting trip . I simply say I'm not going . There is no need to get up on a soapbox and spout off about something I no longer believe in .
In time maybe this persons friend will come to believe in 100% catch and release himself . Bugging him about it or preaching to him will do no good .
This person could simply say to his friend , I'm sorry I would like to go with you but I have a problem with anyone killing fish it upsets me . This would give his friend the chance to say No problem I won't take any when I'm with you , or He could just accept that they are no longer fishing buddy just good friends .