With someone as cringy as DG, a cold attitude goes a long way towards keeping him from being too cringy. Maybe Alex was a dick, but I mostly just remember him being cold. In real life, being cold with someone is the best way to make them cool their jets.
or if you know about their clinginess, don't sleep with them...
The word 'clingy' is too vague to make such a sweeping statement there. It depends if they're "clingy" because they are in love with you and can't live without you, in which case yes don't sleep with them, or if they're clingy because they think you're attractive and are interested in dating. Alex may have thought DG was in that second category, which is why he kept trying to clarify their relationship and asked DG if he was in love with him. He explicitly said that if DG was in love with him, then they should stop. It was DG who lied.
But also I said cringy, not clingy. DG is really embarassing at times, so being cold is a way of stopping him pursuing the relationship socially. We do it all the time. We let conversations run dry that we don't want to continue.
sorry i don't want to offend anybody but Alex is an ass!! Yes, his first boyfriend treated him like shit.... but that doesn't mean he can treat everyone like trash. He doesn't even treat DG as a human being! That's wrong. I love this webtoon. And love the character but can't help but point this out since a lot of you act like Alex is god. Imagine if your bf/gf/fwb (friends with benefit) treated you like that.