I completely disagree.
1) There are a number of pitchers who don't like the rosin or feel that it provides adequate grip. Further, if adding better grip to hold the ball provided a competitive advantage, why is rosin even allowed on the mound?
2) It wasn't dumb. As many former players and current players have said - this is common practice and it provides no competitive advantage whatsoever.
It is an antiquated rule (regarding prohibiting pine tar as a foreign substance - I am not referring to other substances that effect the flight of the ball) that simply has been paid no attention to and therefore is still technically illegal. As a matter of fact, many people are talking about what effect it really had for Johnson to even pursue the issue. The Rays ended up getting out of the inning. Peralta's former teammaters were over hugging/talking with him prior to the game last night and per Rays sources, were apologizing for the incident all together and Johnson himself came out and said a suspension is a bit extreme for punishment. He even feels that an ejection is enough as the infraction is not all that serious. So even he appears to be back tracking on the issue as well.