Why southerner did not want congress to tax money?

I don’t understand the way you wrote the question. But I’ll try to answer it.

Southerners did not want the Federal Government to tax them because the taxes that they were already paying were Slave Taxes. If you bought a slave from a store, you had to pay a 30% sales tax on that slave. And then from henceforth on, you had to pay more then $400 to the Federal Government every month to keep your slave. If you didn’t, the slave was enlisted in the Union Army without your consent.