This is just entirely inaccurate. It is neither legal nor appropriate for the president to “shut down” an investigation into himself or his associates (any associations that would give rise to a conflict of interest), either directly or indirectly. This gives rise to an obstruction of justice criminal charge; the president is not exempt from such laws.
From a legal standpoint, you are simply incorrect. The DOJ, while housed within the executive branch, is a sort of hybrid agency. When an investigation is launched into the president himself, or his business or personal associations, he cannot unilaterally compromise or terminate such an investigation without violating federal laws relating to obstruction of justice.
The only appropriate response to permit the investigation to continue and, if the president is innocent, rely on that fact. Keep in mind that even if the president is guilty of the charge, the only way for that to impact his status as president or to impose any sanctions is for the Congress to institute an impeachment proceeding; otherwise, the violations and sanctions are tolled until s/he is out of office.
I am sorry, but you are simply ill-informed from a legal perspective. I see you doing this sort of thing quite a bit lately, and I would encourage you to avoid making legal opinions or judgments as such. They are not based on any competent understanding of the law, from what I can gather.
I realize that you personally believe that there is no “there there,” but you have been factually incorrect on this count as well. The underlying legal violation — the basis of the investigation — is that the president, while campaigning, was aware of Russian desires to confound the democratic process and a facilitation of Russia’s direct and illegal hacks of the DNC. That is a grotesque violation of the law, if true. Of course, an investigation may also find other illegal activities during its course, and it appears there may be additional legal violations such as money laundering or other illicit financial activities.
I hope this clarifies things for you (although I get the impression that your beliefs are rather intractable, unfortunately).