No response is better than the truth, which may make him angry.
No response is better than blocking, because too many blocks will get his profile deleted.
If you're not interested, the best thing to do is ignore, ignore, ignore.
Some people will simply get mad because they were rejected. Whether it's was a "No thanks" or no response. Some women (and men as well) have told me they got rude emails because they didn't respond. Other women alluded to that in profiles. Saying something like "Don't get mad and call me names if I don't respond." That being said, rejecting someone in a tactless or rude way such as "I don't date fat people" is uncalled for.