It pisses me off that so many people give their friends free passes when they do something wrong, or even ENCOURAGE their wrong-doing. I understand you don't want to hurt your friend's feelings, but when something is up, you need to set that aside and do what's right. If they can't handle that, it's their fault, not yours.
For example, I had to warn my mate multiple times for what he said in the IRC, and I didn't just let it slide because we were going out. I gave him warnings, then personally told him "Nuh, don't do that again, hun. It's inappropriate, against the rules, etc." And he listened and understood. If your friend or mate or whoever has a bitchfit over you politely pointing out something wrong they did and asking them to stop, give them time to cool off and think. If they refuse to listen and stop being friends or block you, good riddance.