It's a gentleness Claudius doesn't deserve, he thinks, but dearly needed when he feels this fragile in himself. Later, he might like Laertes to be rougher with him, to throw him back against the bed and bite at him until he bleeds, or to be such a brat Claudius will have to push him back and hold him in place, or tie him to the bedframe. Right now, he leans back and lets Laertes kiss him like a cherished thing, hands already undoing his own tie and collar, baring more of himself to kiss.