Why do we give so many protections to migrants who claim amnesty in bad faith?

While I am nowhere near a fan of Trump's overall immigration plan, I will say that these idiotic defenses of illegal behavior via "amnesty" are so much worse. These migrants are economic migrants who also are fleeing failed narco states. None of their claims of amnesty are legitimate and the only reason they claim amnesty is to take advantage of international immigration agreements. If these people were honest, they would never be allowed into the United States (or Mexico, vicariously).

So why do so many leftists promote the ruse that these actions are legitimate? They're so illegitimate that the people engaging in the behaviors intentionally lie about their reasons. They're effectively the immigration equivalents of women who make false rape claims. These people muddy the waters, overload the system, and deny migrants who have actual, legitimate amnesty claims their day in court.

If people who oppose Trump won't acknowledge the extremely negative behaviors of the majority of these migrants, they're also engaging in bad faith. Their entire argument is based on, effectively, a lie (that these people have a right to see asylum in the US) which decreases any validity of the remainder of their argument.

Any more leftist-leaning posters on this board want to defend the mass populations using loopholes (their favorite buzzword) to frick over actual asylum seekers? What do you propose we do to thwart these assholes from improperly using our laws meant to protect actual asylum seekers?