That's nonsense. The assumption that all black people don't pay their bills, and the resulting refusal to do business with any black people, is most certainly racism. If they are afraid of people not paying their bills, then do what every other business does - run a credit check, check references, etc.
If a sufficiently high percentage of an identifiable group creates problems, it is sometimes more cost effective to not deal with that group, than to do the extra work to distinguish the good customers from the bad ones.
In a free market, the problem is self-correcting. If the discriminating company is correct, then they will prosper. If they incorrectly pass up too many good customers, then they will not prosper.
Regardless, it should be their right to decide who to do business with. Just like consumers have the right to arbitrarily decide who to buy from.
The owner of the business made it a racial issue when he said he was refusing people in a certain area based on their race and his observation that people of that race in that area didn’t pay their bills.
If he’d dropped the whole racial element and simply said he was no longer servicing that neighborhood, or zip code, or other geographically defined area due to high numbers of non-payment in that area he’d probably be in the clear. The same way pizza delivery drivers don’t go into specific geographic areas due to elevated crime.
The difference is that the geographic part is correlation with race. Saying “colored people” part is causation. Correlation can still cause issues of course, but there’s a big SCOTUS case on it coming up pretty soon.