The downside to annoying Childermass is it only sharpens his tongue, just the same as being annoyed only works to make Lambert even more irritating. He lets out a faint snort when the witcher reddens and gets mad, though that hadn't truly been what he meant to ask. It was one thing of many things, sure enough, but...

"Well, well, it looks as though you really are as easy to embarrass as he was," he follows up, not at all taking offense at the whole not getting possessed to rescue him again bit. That's just common sense, really. "So does that apply to the rest of it? Everything else they did?"

Since Lambert seems so intent on keeping the two versions separate, he may as well follow suit.