No one wants to play devil's advocate. There are some situations where it's hard to play the role of the bearer of bad news, but in most cases where it is hard, it is necessary. The easy route would be to always be the good guy, and telling people what they want to hear. But it takes some serious guts to step outside of your comfort zone and say what needs to be heard. Yes, there will be repercussions occasionally, but more often than not, it will be worth it.
Sometimes we see one of our friends going through each and every day unhappy. We know they're unhappy because they tell us. We can be great friends and sit and listen to them work through their problems, but what if they hit that wall? The wall where nothing changes, things get monotonous and happiness never increases. We, as the friend, may know a possible solution to all of this unhappiness, but in order to convey that idea we might have to be the "bad guy". This means telling them something that isn't easy to listen to, be it a toxic situation with a friend or significant other, or telling them that they might be the source of the problem.
This is where things get tricky. Not many people like to be told something negative about themselves or the situation they're in by someone close to them. But we have to remember that, as their close friend, it falls on us. It is our responsibility to tell them what they need to hear. It would not be fair to hold back and watch the friend struggle when all that it might take to turn them around is some brutal honesty. Tough love is a fine line between being mean and being completely honest. To be honest doesn't imply being mean.
Sometimes, we have to push ourselves to overcome the fear of being the "bad guy". In turn, this can make us better friends, happier people, and more understand of each other. Honesty is rare these days, so don't go around holding it inside your head.