I will take a stab at it.
Here is the problem with the premise of your question: it is not outside the realm of reasonable disagreement. There are no clear cut guides as to what is and is not grounds for removal of the president from office. That means each and every person in the senate has to decide, for themselves, what is grounds for removal. It is a value judgement. And being human, personal considerations will creep into their decision. I do not have to like it, I do not have to agree(and I don't in either case), but to say it is "unreasonable disagreement" is a weak argument.
I think the real reason Clinton was not removed from office had alot more to do with the house managers doing an incredibly ****ty job of presenting their case. When Clinton's lawyer Charles Ruff(who was brilliant and sympathetic arguing from his wheelchair) was able to show that the house managers had people reacting to events before they happened, it was pretty much all over.
With that said, I do think it is important to note the big difference between what Clinton did and what Trump did, and why that, to my mind, should make a difference. Trump misused his office, Clinton did not. The phone call, the withholding aide, all of those are official acts. Clinton's affair and his deposition where he was "less than honest" where done as a private citizen.
As I stated above, it is not unreasonable. Just wrong.
And that is kinda the key. We each have our own standards, based on our own values. When people make these kinda blanket insults("oh, you are being unreasonable", while mild, is still insulting), it stifles actual, honest discussion. And you end up with what we see every day here at DP. I think the standard for removing the president from office should be high, but not out of reach, which sounds as if it is a very different position from you. That does not make you, or me, unreasonable(I hope anyway).
I also think that our founding fathers did it right. The history as I understand it of the phrase "high crimes and misdemeanors" is that it in part recognizes you can't cover everything with laws without stripping all the forests in the world to print law books. You have to have some avenue to cover those situations that are not covered by the law, but are not acceptable. The full phrase is " Treason, Bribery, or other high Crimes and Misdemeanors". Treason and Bribery suggest to me that the founding fathers still smarted from Benedict Arnold. And then they added, essentially, "other stuff". I like that it is nice and general and open to interpretation. It is a good example to me of the idea of a living document, able to change with the times without having to be changed(and hoo boy, that statement will probably be controversial...).
My standard is that if you use the of your office for your own benefit outside of the normal ways(normal ways referring to pay and normal perks of an office). A judege making a ruling to benefit himself should be impeached. A judge making a stupid ruling, not so much. But that is not hard and fast, and there are exceptions. We have to judge each situation based on the unique facts of that situation.
Good thread Harshaw, made me really think.