I don't know which is scarier, that an actual FBI director is suggesting the UFC should train its field agents, or that the media is largely taking the proposal seriously.
MMA is a sport with strict rules for that specific arena, not a complete fighting system suitable for chaotic situations with no time to limber up, civilian clothes (!), no rules and no referee. Many of the moves you'd need to escape such a situation are banned from UFC!
Plus who trained the elite commando units, Mike Tyson?