By the time he gets there, Karkat has decided how to react, which is by going on the offensive.

(The answer is always going on the offensive.)

"NO, I WAS JUST REELING FROM THAT BLATANT FUCKING PROPOSITION, HOLY SHIT. I GUESS QUASI-EROTICA ABOUT COUPLING ON TOP OF A PIANO IS THE SECRET TO DRAWING OUT MOST LEWD AND REPREHENSIBLE KIND OF REMARKS OUT OF YOUR OBSCENITY SQUAWKER. GOOD TO KNOW, I GUESS."