Robert Barnes pointed out this was likely bait to try to get the Defense to object at his mishandling. That way he could say

"Look how threatening this gun is. Unloaded in a courtroom held by an officer of the court it still made people fear for their life. Imagine how threatened the poor protesters felt that night. Its no wonder they reacted so harshly. Kyle brought this on himself, provoking the confrontation by having the gun that night."

Remember their whole case at the end was Kyle shouldn't have been there and he started it by being scary.