That's not entirely accurate; there is a constitutional record of framers arguing not only what should constitute impeachable offense, but whether the power should be granted to congress at all, lest the executive becomes plaything to the House. What impeachment expressly IS NOT, is 'anything congress says it is' as some have opined.
Under any circumstance, lying to a grand jury is a crime. Coercing witnesses to lie, destroy or hide evidence, and to do so oneself to conceal the crime, is obstruction of justice. Unlike the charge Trump committed obstruction, for example, by firing Comey, attempting to destroy or withhold evidence NOT within exercise of plenary power is the textbook definition of obstruction of justice.
Okay, but when you're clearly saying "SOME Christians are idiots" you are qualifying the comment and not in effect saying 'all', correct? Now you have a proper analogy to Trump's comment.
If I say black people commit more than half of murders and a grossly disproportionate amount of violent crime annually, that is an agnostic fact that will get you called racist quickly in SJW circles. If I'm not saying black people are genetically predisposed to violence but your opinion is that I'm racist anyway, that makes you a stupid person, not me a racist.