--Fr. Reginald Garrigou Lagrange, OP
Except, unfortunately, it looks like he didn't actually say this.
Be that as it may. Tolerance was a major theme for Rockwell. It's often been said that "Saying Grace," one of his most popular pictures, was fundamentally about tolerance.
The funny thing about this picture is that it's Christian prayer (not to say it couldn't be some other kind of prayer--just that Christianity is the religion that immediately springs to mind--and the two crosses over Grandma's head don't hurt with emphasizing that, though I know of no critic who has pointed this out) that stands out as unusual. Unusual in the sense that the two young men are clearly surprised to see this public prayer. Unusual in the sense that the man in the foreground appears equally surprised to see it. The public prayer isn't here presented with a kind of, "well, that's just what people do" kind of attitude. It's presented as unusual.
Rockwell lived his whole life up north--New York, then Vermont, then finally Massachusetts. I suppose public prayer may well have been unusual for him. It isn't down here in North Carolina. Even today, nobody ever pauses to look with surprise when nearby people in restaurants pray over their meals! But I grant for the sake of discussion that it would have been unusual, even in Rockwell's time, for northerners to pray over their restaurant meals.
Rockwell's point, then, is that despite the unusualness of the act, despite the surprise of some of the viewers, everyone is respectful. It's about tolerance. We may not ourselves engage in such practices, but we are respectful of those who do.
I myself think there's quite a lot more to the picture than that, but leave that aside. The point here is just that Rockwell took the center of the picture to be tolerance. And he, oddly enough, painted the public practice of Christianity as standing in need of this toleration. You'd have thought that if anything was safe in this country, it would be Christianity!
At least, you'd have thought that back in the 50's. If you are paying any attention at all, you wouldn't think it now. Some of our current crop of tolerant liberals are being very helpfully explicit about their intention of crushing religious liberty. Others aren't just writing about these intentions, they're actively carrying them out. A lot. And trying to make sure that Christians won't have any likeminded lawyers around to help them.
What about the 1st amendment? What about the free exercise of religion?
Oh, that's not what we've got now. We've got freedom of worship instead. If you want to pray, that's fine. (For now. As long as you don't make anyone uncomfortable.) But if you want to live out your beliefs...we can't have that.
This is one of the very few times when I cringe in thinking about Rockwell. It's not his fault, and he couldn't have seen where it was going (though I sometimes think FDR did). But he in some sense bought into this evil reduction of freedom of religion to freedom of worship.