Any reported threat against the president must be investigated, no matter how stretched or tenuous it appears. Even though Volkmann was not using the word 'knock' in a literal sense, it is generally best to avoid any verbiage that could be interpreted as wanting to cause physical harm to the president.
Video embedded below.
"Volkmann prevailed in his most recent Ultimate Fighting Championship bout, against Antonio McKee, this past Saturday in Las Vegas. Following his win over McKee at UFC 125, Volkmann was interviewed by MMAFighting.com's Ariel Helwani. At the end of the interview Volkmann was asked whom he would like to fight next.
Volkmann replied that it didn't matter, then added a political message deriving from his professional experience as a chiropractor: "Actually, Obama. He's not too bright.... like the make a home affordable plan and his health care plan, someone needs to knock some sense into that idiot.""