I said before that this arc felt somewhat lighter than some of his earlier plots. What you said is true in that sense. But I think in the bigger picture this wasn't so different. From an objective pov he suddenly barged in and ruined the dude's long awaited confession scene. If the situation hadn't been so special, that would have been an unforgivable douche move. Even under these circumstances it was quite nasty because he did it without informing anybody else beforehand. Hard to see any other more shocking solutions to the problem. I reckon Yui and Yukino can't anymore judge his stunts case by case. They are growing tired of the fact all of his deeds are like this if not worse.