He said that Black churches served as a national reminder of an American promise of equality; and suggested some wanted to see that equality eroded.
"It's an idea that we can't abandon. And some want to see it abandoned."
He spent the weekend courting Black voters and trying to draw a contrast with his Republican predecessor and likely challenger on subjects such as voting and abortion rights.
"Trump and his MAGA friends are determined to take away your freedoms, like the freedom to vote. Trump brags about taking away a woman's freedom to choose. And now they're hatching a plan for a national ban, a national ban."
And he criticized Trump for a recent incident where the Republican appeared to confuse his primary challenger, former South Carolina governor Nikki Haley, with former Democratic House Speaker Nancy Pelosi.
"By the way, have you noticed, he's a little confused these days? He apparently can't tell the difference between Nikki Haley and Nancy Pelosi."
He wasn't the only one in that state taking shots at Trump. Haley, who has so far failed to win a single Republican primary, on Saturday also brought up her rival's apparent mix-up.
She also called him "tired," "totally unhinged," and challenged him to meet her face-to-face in a debate.
Trump has refused to participate in any of the Republican nominating debates and is refusing to debate Haley.
DONALD TRUMP: "I'll tell you what, I feel sharper now than I did 20 years ago. I really do."
In remarks from Las Vegas, Trump pushed back on reports about his recent gaffes and said Haley would be a much weaker Republican candidate.
"The radical left Democrats want Nikki Haley because they know she's the easiest person to beat. And she will, she doesn't have Republican support."
Trump and his allies have begun a campaign to force Haley out of the race before the next major vote in the primary contest, in her home state of South Carolina on Feb. 24.
Haley has pledged to keep campaigning in South Carolina and beyond.
