I mean... I think it would be easy to list professional players who would be suitable for teaching new players, and not the other way around... haha, but let's get to the mission!
Everyone here is pointing out players who have explosive and sometimes disrespectful or unpleasant attitudes at the table... Based on this principle, I believe we all agree with Helmuth... I also think Martin Kabrhel would be terrible following this line of reasoning. hehe
Anyone else that comes to mind? I don't know, maybe Tony G? I have the impression that he's a spoiled player who wouldn't pay much attention to people learning.
Anyway, these are just abstractions...
Besides that, I can't think of anyone who COULDN'T fulfill such a role, I mean... Some would probably have better teaching methods than others, but I believe everyone has something to add when we're talking about professionals... Even those with unpleasant attitudes!