That is a very valid concern, enough that Steph gives it a few seconds of thought instead of immediately making another joke. She doesn't want to thank Bart for his hospitality by putting a hole in his wall.

"Probably Jason, he's got a temper. Cass can be competitive, too, but if it gets outta hand we can toss them outside, or give Kon permission to scruff anyone who needs to be scruffed."

TTK is useful for that, after all.