The irrepressibly wacky legislator from Knoxville thought it would be hilarious to post a "humorous" graphic of a pressure cooker as a weapon. Because, you know, those murderers in Boston used bombs made from pressure cookers, so ... funny, right?
His point, if you want to call it that, was to illustrate the hypocrisy of the left for calling for gun control after the Sandy Hook shootings but not calling for pressure cooker control after the Boston bombings. Or something.
It's all too tiresome to explain further. If you really must read his rationale, go to his blog, which is probably what he had in mind anyway.