Clipper Darrell KO'ed In Altercation At Clippers Game ... Video Shows

Clipper Darrell -- the most famous L.A. Clippers fan -- was knocked out during an altercation at a game on Monday ... new video, obtained by TMZ Sports, shows.

In the footage, you can see Darrell -- real name Darrell Bailey -- in his famous half-red, half-blue suit ... standing with a Crypto.com Arena security guard following the Clippers' game against the Boston Celtics.

The two seem to be in some sort of argument ... where the man wearing a red polo appears to be preventing Clipper Darrell from moving through a concourse at the NBA arena.

At one point, the man can be seen in the video putting his elbow near Darrell's neck in what seems to be an effort to keep him from advancing. Darrell, the…