Relay operators are as free to choose what they want to store as users are to choose what they want to see. Free relays are free only for the users, they have costs for the operator, and he has the "freedom" to minimize those costs by cutting off spam!

What operators should not do is do is hide this from users. If you operate a WoT relay, be open about it, and about whose WoT it is.

You do not agree with the relay rules, you have thousands of choices to choose from. Jus don't use the WoT ones.

That said, it still a bad implementation to avoid spam. Too many downsides. It is valid only as a strategy to reduce costs, or if used personally by the operator because you couldn't find any web clients that implement WoT (my case).