I know, being honest can sometimes be very difficult when the issue could end your relationship. But that is the whole point, truth does hurts!Being honest with your friend becomes a tug of war of morals and salvaging what you are afraid to unveil. But there is actually a way to tell the truth and being honest.
1. Honesty is the baseline- when you want to confront, be respectful to your friend and phrase your sentence nicely and politely. Or, just be casual!
2. Remind your friend that you are doing this because you respect them, and not because you want to conspire against them. Also, you want them to change for the better.
3. Respect the way your friend accept your comment. DO NOT JUDGE THEM BY THEIR RESPONSE TO YOUR COMMENT! If they want to be mad or upset, LET THEM! Because, being a good friend is being honest and be there when the honesty was blown to their face.
Bottom line here is, if your friend did something wrong, correct them. They maybe don't realize it. Like the old saying goes, one's mistakes can only be seen by others. All you need to do is talk! words can be really powerful. If you continue talking behind their backs and keeps planning conspiracy, then nothing will be solve, matter will just get worse!.
Why go and tell everybody you don't like their actions, when the solution is just go and tell them?