He does have something resembling a point, though that's less a defense of Trump and more an indictment of Obama. Some of the bad things that the Trump administration did/is doing started under Obama, or even earlier. For example, the inhumane treatment of interned illegal aliens?
That happened under Obama too.
But like I'd said earlier, the fact that Trump is letting this continue doesn't reflect well on him. Yeah, I'm against illegal immigration, but I'm also in favor of treating detained illegals more humanely.
And in any case, Trump's done enough shit on his own that I can't say I agree with Dorsey. Obama didn't demonize illegal immigrants as drug-dealing rapists, for example.