How is blocking a magma fist with his bare hands not proof of haki? Do you maybe think that Jimbei is lava proof or something?
You can see here what happens to Jimbei when he is caught unaware by Akainu's magma fist
http://www.mangapanda.com/one-piece/578/9 but in the panel I linked (
http://www.mangapanda.com/one-piece/574/5) You can see the magma fist doesn't burn right through him, heck Jimbei's hand even looks like its colored black (which could arguably be the first time Oda showed colored haki if you think about it). And please don't say something weird like Jimbei coated his hand in sea water to block the punch, we already saw Akainu's magma fist instantaneously evaporate a massive amount of ice so wet hands would be no issue to him.