The IRS isn't morally acceptable. They financially ruin people and businesses all the time. Keep your hands off others income you rats.
Discussion
I have seen people go incredible leaps in logic to not only justify the existence but worse, defend the benevolence of such institutions. As if they are the only thing holding the line against a dystopia brought on by greedy corporations and fraudsters...madness.
Not the IRS that's immoral. It's taxation. The IRS just enforces the immorality. Kinda sounds even worse when you put it that way.