It's unusual that I say this about your posts, but I think this time you really blew it. Your point is good. It just doesn't hit the mark. What Obama's executive order did had little if anything to do with keeping guns out of the hands of the mentally ill. It put 75,000 people on the NICS's "no guns" list simply because they indicated to the Social Security Administration that they needed some kind of assistance with their finances. This could mean that they needed someone to take their check to the bank to deposit it or it could mean that they were mentally incapacitated to the extent that they could no longer handle their finances (and if addled to that degree, should probably not possess a gun). However, there was no way to determine the degree or type of impairment. Then, as has been pointed out, the order amounted to the deprivation of a Constitutional right without due process or even notification.
I think the order was just Obama's feel good effort to add to his legacy.