Alright, before this devolves into a bunch of stoopidness, I think the idea behind bans or suspensions for headhunting or dirty play has a lot to do with repeat violations. Since we can't ever prove intent, all we have to go on is performance tendencies. Let's not cherry pick one hit over a 5-year career and pretend we're comparing apples to apples. For anyone actually interested in comparing Chancellor and Matthews, here are the fines and penalty stats.
One of these guys appears to be playing more cleanly as his career progresses. The other, not so much.
FINES
Clay Matthews
2014: NFCCG, blindside block.
2013: Week 13, helmet-to-helmet. Week 10, roughing the passer. Week 1, late hit (This one was ridiculous. He hit Kaep not just when he was out of bounds, but when the QB was beyond the white area. That's 6 FEET out of bounds when Clay launched himself toward Papaki's head.)
2012: none
2011: none
2010: Week 3, facemask
2009: none
That's 4 fines for illegal hits in the past 2 seasons.
Source: Spotrac
Kam Chancellor
2014: none
2013: Week 17, late hit (No excuses, but this was an exceptionally testy game against the Rams, which are usually all-out brawls to begin with. Kam's was the only Seahawks fine versus 3 fines – 2 of which were helmet-to-helmet – and an ejection for the Rams.)
2012: none
2011: Week 10, hit on defenseless player. I think there was one in week 11 also, but it was repealed because it was actually his shoulder and not helmet that made contact with Lance Kendricks' head and the contact wasn't initiated at the head.
2010: none
That's 2 fines in 5 years. That's not a repeat offender.
Source: Spotrac
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PENALTIES
Clay Matthews hit-related penalties
2014: Week 7, unsportsmanlike conduct. Week 10, unnecessary roughness.
2013: Just the ones that were fined.
2012: none
2011: Week 7, roughing the passer.
2010: The fined facemask.
2009: Week 12, roughing the passer.
Clay has had 4 hit-related penalties in addition to the fined hits. 2 of them last year.
Penalty stats from Pro-Football-Reference.
Kam Chancellor hit-related penalties
2014: none
2013: Week 15, personal foul.
2012: Week 16, unnecessary roughness – this was the soul-stealing hit he put on Vernon Davis, which was shown to be clean.
2011: Week 3, unnecessary roughness. Week 7, unnecessary roughness. Week 11, unnecessary roughness.
2010: none
Kam has had 1 hit-related penalty in the past 3 years and 1 more that was shown on replay to be clean.
Penalty stats from Pro-Football-Reference.
He had 3 hit-related penalties in his first year as a starter, then made great efforts to be more precise with his tackling. That's a sign of someone trying
and succeeding to play cleanly.
Here's an article from NJ.com explaining his conscious efforts to play within the rules.