I'm a bit confused by this. Suarez was not charged with bringing the game into disrepute, so why should his punishment be in line with those who are? Now if you think that is what he should have been charged with, and 5 games is the correct punishment, then fine.
Also there is a difference between an act being deliberate and being premeditated. The bite was not an accident, so it was deliberate, but I highly doubt, and I don't think anyone has suggested that Suarez planned ahead of time to go and bite the big Serb. So the comparison with Keane seems to fall down.
The only precedent we have is the Defoe bite some years ago, but it went essentially unpunished as the ref issued a yellow card at the time. Other than that we have to look at what Suarez was charged with, Violent Conduct, and ask which cases come close, and see if the punishments compare. So far I've seen non that seem equivalent to the bite, or come close to 10 matches, so it seems the FA is treading on new ground here.