The No-Crime, So No-Obstruction Argument About Trump

I've heard from more than one opinion source that it was ridiculous (I think Senator Lindsey Graham used the word "absurd") to consider whether Donald Trump was guilty of obstruction during the Mueller investigation into the extent of Russian interference in the 2016 and whether Trump or his campaign conspired with this adversarial foreign power.  Since the final report stated that there was insufficient evidence to charge the president or his campaign with conspiracy, some of his vocal supporters are claiming that since there was no crime, then how could he have been obstructing the investigation of one?  The logical fallacy of such an argument is easy for me to see...let me explain...

If I am pulled over by the police for a traffic violation that the officer later decides not to ticket me for...but I am uncooperative and disrespectful during our interaction and, say, call his boss to get him to back off or try giving a bribe, that officer is justified with charging me with resisting an officer...tantamount to an obstruction charge.   Sitting there screaming "witch hunt!" or "hoax!" and personally insulting the officer likewise mitigates against me...as well as not presenting my current driver's license or auto registration. Never mind that the original charge is dropped...I've created a new one by my subsequent behavior.  Now to Trump: there are two periods for which his behavior has been scrutinized and reported on: the original target of the investigation, that is the 2016 election campaign, and then the investigation itself.  It matters not what the final results about 2016 are...the question is whether Trump improperly interfered with the investigation itself.  And that's where all the hullaballoo about "obstruction" is coming from.  But of course, if you're a "forever Trumper", unquestioningly believing carte blanche anything he says because he's your idol above all idols and is standing firm against all those evil communist Democrats, you'll never believe anything negative anyone says about him...or even what you see and hear with your own senses for that matter.  I am no expert in the law, but at this stage the obstruction question seems more a political one than a legal one, anyway...it's all in the hands of Congress to deal with according to the Constitution, something that our president seems to have a great deal of difficulty grasping...