I would tend to agree with the statement "IF ever there were a dictator in the White House, he was it."
There is not question he kept Maryland in the Union with some pretty heavy-handed tactics. Nobody is denying that there weren't political prisoners.
But notice the difference between your statements and the silliness Thomas is spewing. You actually are giving some facts and figures, he just makes absurd claims that EVERYONE opposed to Lincoln was arrested. That obviously did not happen. When called on it, a rational person would have just said, "okay, yeah, I was engaged in hyperbole there." A conspiracy theory nut just digs in and insists the absurd is somehow the truth.
If he had been content with saying that Lincoln wasn't shy about clamping down on dissidents, I'd have agreed with him. If he had said that Lincoln wielded more personal power to exercise direct government control over the country than any other president, he might well have been right. (Although people don't realize how authoritarian Woodrow Wilson was during WWI. Lincoln probably has him beaten, but that's neither here nor there.) But no, true to extremist form, we can't be content with logic or facts; it has to be out on the fringe. So now we're asked to believe that Lincoln was a dictator who was arresting millions of people. Give me a break!
Now while I personally think you're engaged in some overkill and hyperbole with the characterization of "vicious," you're not being a conspiracy theory net. You're taking a strong stance. I don't agree with it (if it makes you feel any better, I'd agree to "ruthless"), but at least you're backing your stand with some actual facts. You're not making claims that are impossible on their face.
I would have thought Richard Nixion was a better choice for this role, and J Edgar was a pretty good manipulator of your laws and politians for 50 years