People dislike him as he is good, not the best thing sliced bread but a good player. Plays for Wigan, usually people other than Wigan fans love to hate Wigan. Put the two together and it's not surprising.
Peopl calling him a cheat is a bit strong, cheating is like the betting scandal of Long and Gleeson.
There have been plenty of players who have bent the rules, pushed the refs and tried their best to gain a competitive edge. Sinfield is constantly in the Refs ear at Leeds. Long was always trying to push the boundaries of what was acceptable. McGuire was always playing for the penalty. Tomkins does the same, he is not cheating.
When players in the '90s started to thrash around in the tackle (playing for the holding down penalty) were they considered cheats??
I feel Tomkins treatment by fans and the league is a little stupid and some people are getting rather silly about a young player who is good and even stated by opposition fans as being only good, so why the abuse by fans and some players? Crazy, he's not that good.