Monday's visit to Arlington National Cemetery by former president Donald Trump was already causing some grumbling ... over concerns that the hallowed grounds of a military cemetery were being used for political purposes.

But then came reports that Trump staffers got into a verbal and physical altercation with an official at Arlington ... who was attempting to stop those Trump staffers from taking pictures in a restricted area of the cemetery.

Now it's a full blown controversy.

Paul Rieckhoff is a retired Army infantry officer and combat veteran of Iraq ... 20 years ago he founded the Iraq-Afghanistan Veterans of America ... and went on to found the Independent Veterans of America.