Can someone give me a rational reason President Trump should be impeached?

He is encouraging foreign interests to get involved in domestic issues, specifically in an attempt to further his own interests over the best interests of national security.

That's really all you need. There are other things he's done that are clearly covered by high crimes and misdemeanors. This is as simple and as rational as you will read.

And yet, folks will claim that it's a smear campaign.