Trump: The emoluments clause is 'phony'

Just where does it say that a President cannot make a profit in his business while entertaining leaders of other countries? I understand how that can potentially be a dangerous thing, but with sunlight shining on it, like there is nowadays, I do not see a problem, and I definitely do not see a prohibition of it in the US Constitution.

Article I, Section 9, paragraph 8 prohibits the acceptance "of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State." It does not prohibit making money from your own personal business. If Trump owned an ice cream store. Though he would more than likely offer free icecream to a visiting dignitary, he would have no obligation to take a loss by giving free icecream to the dignitary's whole entourrage, security detail, etc. It's no different here.

"Emolument" is defined in Webster's 1828 dictionary (nearer to 1778 than modern dictionaries) as:
1. The profit arising from office or employment [not personal business]; that which is received for compensation for services, or which is annexed to the possession of office, as salary, fees or perquisites.

In other words, a President may not be employed or hold any office under a King or Prince or foreign State for which he is salaried or compensated, even if only receiving a percentage of a fee that such King, Prince or foreign State has power to charge.
This sets up a definitive wall of separation between he who the people of the United States have entrusted with an office of public trust and foreign leaders who, otherwise, could employ a citizen of the United States.

The same is true with regard to the other emolument clause in Article II, Section 1, paragraph 7, which forbids the President from working for any other agency of the federal government or any agency of any of the several states while in the office of the presidency.