It comes off as being insensitive to gay people to tell them to just stick to being straight, even as a joke, because there are many people who will say the same thing but in a hateful way.
For example, my mother says I should try out being with men whenever she sees me broken hearted, and while she has good intentions, it also means to me that she doesn't quite believe that I can only like women and sees being gay as a phase. And it's upsetting despite what tone she says these types of things in.
Saying horrible, incentive stuff, to your close friends, is a guy thing. One time, my mother over heard me talking, with my friends. She was appalled by what she heard. Afterwards, she asked me do you guys even like each other?
My point is guys loves teasing his friends, no matter they're male or female (Oh and especially when they know you failed to approach a girl, you're done for with them).
To outsiders, that can be seen as heavily offends, but to the "offended" person it's just casual joke.
As you can see, the guy in this manga just an idiot type of friend, he couldn't even read the mood and the other girl had to drag him out.
Hell, this is the first time I justify for a guy in yuri
