'No Kings' Protester Arrested for Allegedly Stealing Glasses Off Trump Supporter's Face in Viral Video

10/21 3:45 PM PT -- Denver Police clarified to TMZ Tuesday ... the man arrested this weekend, Jose Cardenas, is actually the person suspected of stealing the victim's glasses off his face ... Cardenas is not the man suspected of tripping the victim in the street.

A Denver Police rep said ... "Cardenas is now under investigation for Theft from a Person and not Second Degree Assault." The person who tripped the victim remains unidentified, and police are asking for the public's help in identifying him.

A "No Kings" demonstrator has been arrested after cops say he's the guy who tripped a man who yelled out a gay slur at protesters in a video now going viral.

Here's the deal ... video is going around online capturing a moment from the protest that took place in Denver Saturday -- where you hear a man cheering for the president while flipping off "No Kings" protesters.

His antics reach a fever pitch when you hear the man use a gay slur ... yelling at someone, "Ride your bike you f***ing f**." In the video, a young person holding a skateboard then appears to steal his glasses and tear off down the street.

You see this man give chase ... and, it appears he slips and falls hard in the street -- before getting back up to give chase again. After he's run a bit farther, it looks like he's tripped by someone and hits the ground hard.

Police say they've now arrested the person they believe tripped him ... a 20-year-old named Jose Cardenas. They're alleging he "caused a serious laceration" to the victim's head.

Cops say they showed Cardenas to witnesses of the incident ... and they say those witnesses identified Cardenas as the person responsible. He was taken to the Denver Jail and charged with aggravated assault.