"It won't take too long! And it's no bother, honest!" His expression is reminiscent of a wounded puppy as his eyes practically water.

Despite your insistence, he wanted to heal you. You'd rejected Marcille's healing flat-out, claiming that her mana was too valuable to be "wasted" on you. He didn't agree with you. No one else agreed with you either. And everyone had insisted that it would be better if you got healed after acting as a shield during a particularly nasty battle.

But you'd still been standing there, repeating your sentiment that you didn't want Marcille's mana wasted on you. So instead, Laios had begun vouching for his own healing instead. He'd practically hounded you down during the rest hours, claiming that he didn't mind spending some of his mana since he wasn't in the habit of using it frequently anyways, so he wasn't putting anyone at risk by using his, especially not when he was about to rest and replenish himself anyway.

He remembers what a cornered animal looks like, and it doesn't feel reminiscent of your current pose despite our nature as a Beastman. If anything, you seem to be more in control of the situation than he is as he seems barely a second away from getting on his hands and knees while flat-out pleading. He's not sure what you're reasoning is to deny yourself the healing on the basis of wasted mana, especially not during a situation where there was really no other imminent matter that needed the usage of mana instead.

He sees this as irrational, stubborn behavior that he's hoping you'll drop if he begs hard enough.