It doesn't matter if it is defensive or offensive in nature. A forearm to the head or neck is going to be a technical foul and usually an ejection if it is determined to not be a basketball move. There was no ball for him to be going for so definitely not a Bball move.
This is a Bball game and not a street fight. Putting arms up is fine, but he pushed with the arm was not. If he just puts his arms up and continues down the court nothing gets called. Atiki put his arms up then pushed off, since his forearm landed in the head and neck region he got ejected.
Not long after this Lonher had a similar situation except Lonher just kept on going with his arms up.