Earlier quoted context omitted.
What would you say is the right behavior in that situation, then?
You have to know the person to be sure they are ok with it. If there is any uncertainty then don't be honest about what you think, just give the standard advice like "Just be yourself" or "You are wonderful, just haven't found the right one yet!". The alternative is to just be brutally honest and that way filter out friends who aren't ok with it. It might hurt a bit, but if you value this kind of communication over h…
I found the inverse to be even more valuable. Finding friends who are not afraid to be brutally honest with you when the situation calls for it is difficult, but worth it so much. Just make sure you actually can receive this kind of criticism first without taking it as a personal attack.