First you’re putting words in my mouth. We are talking about petty crime not the entire law, and we are talking about prosecution not all enforcement. Prosecution is not the only way to enforce the law, so nobody is talking about “no enforcement”.
And the statement is because it is a falsifiable with no evidence to back it up. Wegner’s statement about plate tectonics was bold by the same measure (although he offered some evidence; but apparently not enough).