A perfectly reasonable response would be
"Look, there's a gazillion twats out there. We're doing all we can but with the best will in the world it's an impossible task to stamp it all out. We'll do as much as we can but the truth is some people will slip through the net and some very blatant cheats will get away with it for longer than we'd like"
What the lichess guy actually said on perpetual chess this week was, words to the effect of,
"Look, we've thought of all the ways anybody might try to get away with cheating occasionally and we'll catch them all"
- which is self evidently not true. And therefore much worse than doing nothing.