Wrong! The NRA simply pointed out to him how the background checks or red f**g laws opened the door to such abuse as to render them practically unenforceable from a constitutional standpoint.

As proud republican here on OPP pointed out, what constitutes 'mental illness'? It could be persuasively argued that nobody is free from mental illness. Just as nobody is truly free from physical illness if an examiner is hell bent on finding some malady.

Trump's priority is to make America great. An armed citizenry is the best defense against tyranny. Trump knows it. The NRA knows it. Opening the door to unconstitutionally taking firearms away from citizens by expanding background checks is not the answer.

Universal background checks are a joke. Do you actually think that criminals are going to submit to one? The SCOTUS has ruled, in Haynes v US 1968 that a criminal cannot be prosecuted for failure to submit to a background check or to register a gun because to do so would violate their 5th Amendment rights.
https://bearingarms.com/tom-k/2017/12/22/want-know-gun-registration-doesnt-impact-criminals/
There were more than 100,000 stops on gun purchases in 2017 alone. While a good number were mistakes, tens of thousands were not.
https://www.usatoday.com/story/news/politics/2018/09/06/gun-laws-report-finds-few-rejected-during-background-checks-charged/1213216002/

117,000 plus fails. 12,700 fails recommended for prosecution. 12 prosecutions. So your answer is to penalize people who are not going to commit crimes in the first place. Typical Liberal logic. While you're at it, why not stop drunk driving by revoking the licenses of non-drinkers?
Yep. We already have a bunch of laws that aren't enforced, and you Liberal Hobbit fart sniffers think that the solution is to enact more laws that won't be enforced, or even obeyed except by people who aren't going to commit crimes in the first place.
Way to problem solve.
Oh, wait! You can ban the tens of millions of semi auto rifles in this country that were not used to commit crimes. While you're at it, how about banning the knives that murdered more people than the rifles? Or the clubs, or bare hands?
OH wait! There is always banning magazines of more than ten rounds. Good luck with that. How do propose to get rid of a couple of hundred million of them when you don't even know who has them, and by the way, there is a Constitutional prohibition against ex post facto laws. Don't know what that means? Look it up, or find someone who can actually do research to look it up for you and explain the big words.