That's the point he was making, Colossus can hang with him because he can take his punches, not because his own punches will be knocking him silly.
And I doubt current Warpath is strong enough to put enough force behind his knives to pierce or cut Colossus. However, once Ares kills him, he'll toss Colossus the knives, and now Namor gets shredded.
Is it just me, or has anyone noticed Ares getting a massive boost lately? The guy just took out X-Men, and walked through time.