How about 

"Prefer methods over class constants. This eliminates the danger of
constants being redefined or their values being mutated. While freeze
can partially mitigate this producing a new value from a method each
time is safer."

I hold the opinion that there is never a particularly good reason for any class method (apart from `.new` of course). Class methods are just namespaced procedures, they resist refactoring and should be avoided in OO systems.

I'm prepared to remove the anti-class-method sentence and we can argue about it in the pub sometime.