Considering that part of what Emil had been bred for, originally, many centuries ago, had been tracking down or warning for werewolves (which he was never sent off to do, because other undead had ended up a bigger issue than werewolves at that point. Probably why Emil's still around), it's not really surprising that he takes offence with Joker's everything.

He calms down a bit when both men seem to so obviously be at ease and not about to go anywhere, and well, being ordered to stand back on top of that, but he keeps a wary eye on Joker as he returns to Ragnar's side.

"Yeah, I'd prefer if you could keep them out of him. Bites get infected so easily." ...Ragnar isn't actually this calm, as much as the words are said lightly, picking up Joker's cheerful attitude. But he's darn good at faking it.