Acroy does have one valid point, I think, which is that collusion is hard to prosecute. Proving it is easy. Doing anything about it, when it's the President, is basically impossible.
I suspect that Mueller will present an ironclad case, and it still won't matter. My prediction is that Trump personally directed his campaign staff to coordinate with Russia to undermine US foreign policy in exchange for their help in swaying the election, and that this will be backed up by multiple witnesses and a trove of corroborating documents. Trump will deny it, of course, but the standards for criminal conviction will be easily surpassed. A crime was clearly committed, he had motive, opportunity, and means, and everyone interviewed will agree it was Trump as the ringleader of his campaign's misdeeds.
And after the nation's highest law enforcement agency presents absolute proof of multiple crimes, nothing will happen. Trump's comment about shooting someone in Times Square is ringing more and more true. He'll go to McConnell and Ryan and privately say "Yes, I deliberately broke six different laws in this election, but you need me and we all know I'm untouchable, so get down on your knees and suck it." And they will. They'll gladly keep a known traitor as President, to support a political agenda that they know most the country hates.
And without Congress to take action, the President is basically immune. He could literally murder his family in the white house tonight and stay President. He could send a tweet that reads "I colluded with Russia" and stay President. He could go on 60 minutes and admit to obstruction of justice, and stay President (wait, that last one already happened, bad example?).
America is a vast nation full of natural resources and profitable businesses and hard working citizens. Our greatness does not lay in Washington DC, but across our lands. At the moment, the reigns of power have been seized by small cadre of profiteering zealots but this is a temporary situation. Elections will eventually set us on the right path again, or they won't and America will fall. You can't do much about it either way, as we are all sort of along for the ride in this great experiment. So vote your conscience, as often as possible, and try to accept that sometimes the system will fail. Sometimes I think that in cases where our electoral system is so easily subverted, that's a sign of weakness in our system and maybe it should fail. If Russia can so easily tear America apart, then does America really deserve to lead the world anymore?