This is a frequently-used structure by Schulz at the moment. It goes:
1. A character does or says something silly.
2. Another character, or in the case of Snoopy vs. The Yard plain old physics, shows why the thing done is silly.
It's not much by itself, so these strips usually have something else going for them, either funny art (as here), empathy with one of the characters (such as the silly one who realizes by the end his mistake), or in some cases the silly character bullheadedly persisting in his error regardless. This happens with Lucy a lot, but Linus also becomes susceptible to it, every Halloween....