I know there was the physical scene associated to "I have the high ground"

....

But I had always though Obi Wan (ever the teacher) was addressing the moral com. This duel happened after Anakins execution of the younglings. Anakin had lost all direction. His turn to the dark side was almost complete.

Obi wan's "high ground" was a final plea and perhaps a verbal justification for destroying what Anakin had become.