It looks like some presidents can be easily killed even with a knife. If the guy had had a knife, he would have easily stabbed her if he was a bad guy. Going by cues, it seems the dude has mental issues or was deported from the USA and was trying to pass the message to Madam President. On her part, it seems the President embraced him, and it looks like she enjoyed the brief grope, and that is what the security detail read quickly. That is why they didn't unload the violence on his lame ass!