Although I can understand that you are upset about this and maybe under your state law the touching could constitute assault, I think that you would be spinning your wheels if you try and prusue the issue.  Yes, mall security is not eh police.  But they do have some authority to protect those within the confines of the area they protect and so I think that there may be a fine line here as to a perceived threat.  I would speak with a personal injury attoreby in your area on the matter giving more details of the situation.  The consultation should be free and there could be details left out that could spin this matter in your favor.