Yuri is frustrated and full of rage, doesn't know how to deal with this, and needs to blow off steam somehow. He decides he wants to do it with Viktor. Viktor is flabbergasted with his demands, but doesn't know how to say no to Yuri, a person he considers a lot, who he holds a lot of affection and admiration. Yuri takes advantage of that.

(And Yuri isn't considerate or delicate at all.)