As I said in the previous comment, I've personally met people whose lives were ruined by people being "tough and straightforward". These people struggle to identify and address their problems, because they unwillingly think back to the unfeeling and cruel way they've been treated. Even the nicest, most considerate conversion will be extremely anxiety inducing, because it is filtered through their bad experiences.
Insecurity is one of the most common problems that people have when identifying their weaknesses, and being direct or tough runs a high risk of increasing these insecurities.
Being nice isn't the best approach in every situation, but I would say it's a safe default to pick when you're uncertain about the cause of someone's problems.
I'd also warn against using the term "loser" so loosely. We need to consider by which metric we determine someones life to be suboptimal, and the certainty we have in that metric. I think we both agree that maximum human happiness should be the goal to strive towards, but getting there is pretty tricky.
Let's imagine a person that works at McDonald's for their entire life, has no friends, and spends all of their free time playing video games while high. Said person has spent many years searching for their optimal path in life, and they found every one, except the one they are on now, lacking. Most people would call this person a "loser", but are they really? After all, they seem to be on a path that optimizes their happiness. Telling that person that they are a loser may cause them to "improve" in the eyes of the average person, but they will, in reality, change their life for the worse. They may be successful, but they'll also be miserable.
Whenever you judge someone else using your own personal version of an optimal life, you run the risk of being wrong and forcing that person into suboptimality. We can try to determine things that are likely to increase someones happiness, but the word "likely" is important here. General assumptions about a "good" life tend to be risky, because humans are quite complex, and determining someones best course of action from the outside is always extremely difficult and error-prone.