I'd earlier made this point. The key

And the reason it is easy for you to forgive such fools and think well of them, Mr. Potter, is that you yourself have not been sorely hurt. You will think less fondly of commonplace idiots after the first time their folly costs you something dear.

In the Wizengamut:

But by then he'd (Harry) already declared war on the country of magical Britain, and the idea of other people calling him a Dark Lord no longer seemed important one way or another.

When their idiocy threatened something dear to Harry, he declared war on them. Mission accomplished. I've been wondering if Harry is ever going to remember that conversation. It's just so obvious. All that's missing is the "told ya so" speech from Quirrell.