The link that was posted gave context. He wasn't trying to disarm the population, he was talking about confiscating a firearm from someone who's been flagged as about to harm themselves or others.
In your own damn link it says he was talking about those who are "red flagged", or is alerted to authorities as someone who might do something. You know, like when someone posts a manifesto online, he was saying they should be able to confiscate their gun and then have the court process.
He certainly wasn't saying he wants to disarm regular citizens.
There was no law changed to call them illegal. It's not like they were here as citizens and then trump came in and revoked their citizenship. They entered illegally and have always been illegal. That's the major difference.