"Since it does rather reflect back on me, doesn't it?" Mycroft went for the obvious answer. Sure, it was an absolute lie, but Sherr wouldn't pick up on it the way Sherlock might. They didn't know each other's tells enough for THAT.
"And good. I just hope it keeps you that way. Believe it or not, I don't like having to be the one attempting to smooth things over when my family are in trouble. Sherlock is quite enough on that front,"