I've never understand this statement in reference to "The Turk". They show how he is good with a knife but I may just not realize how this part is explained by the following events. Turnbull can you or some explain?
Tom wanted Vito to make a deal with Sollozzo. I think he was trying to assuage Vito by explaining that the Turk would be a reliable business partner, not a quick-to-kill hothead. From Sol's viewpoint, killing Vito was "a matter of business with a reasonable complaint": Vito's refusal to give him police/political protection in return for a big share of Sol's drug profits was preventing Sol from doing business.
