Marco wanted a little bit of emotion, he got a lot more than that after running with scissors and more importantly, he was suppossed to actually do the right thing.
Being with Jackie who got him to ride a skate, something he had never done before and that apparently scared him due to fear to fall and look like a dum-dum, was something she broke without much effort, without pushing him by force or with magic. That's exactly what Star does, she doesn't ask, she doesn't request, she just does and more than once we have seen Marco's body being hurt because of that.
How come they didn't realize a guy would NEVER, ever be anything but a friend of a girl that was so nocive? She even was coward enough as to just shot him at his back, for fucks sake, attacking on the back, kick slamming, or elbow dumping, is only something you do with bro-friends!