Perhaps the strongest argument in Trump's impeachment trial is the fear of setting a bad precedent. It should be taken seriously. When I studied American government, the idea that a president could ever be impeached was not a serious issue. When Watergate occurred there was a quick surge of research, trying to figure out the pros and cons, the procedure for impeachment.
We went ahead with the process to impeach the president. I haven't researched, but I'd guess that some serious people then said it was unlikely there would be another impeachment in the 20th century. But there was.
We went through the Clinton impeachment--that experience plus some changes in social mores may have set another precedent--we don't want another impeachment over private behavior, and hopefully future presidents have learned to handle scandals better.
So now we've impeached Trump twice. I hope the precedent we've set is never to elect a person like him again.