I am 100% for users to obfuscate. I am 100% against miners using it. Having said that TOR mining wouldn't be desirable for commercial mining anyway. Centralized open competitive mining is optimum for consumer protection and global participation.
Why do you think it isn't a good thing that miners mine anonymously? (Not implying that Tor is safe btw)
Do you not think it makes Bitcoin more censorship-resistant?
Do you remember the aborted CoinValidation startup? (The one that basically wanted to make a business of destroying Bitcoin's fungibility by wanting to blacklist certain categories of coins on opaque criteria)
Do you think it is good that miners are only a handful of identified entities that governments can pressure to refuse to process transactions on criteria other than economic ones?