I've never heard Arngeir talking about Ulfric's usage of the Shout. Especially not in such a double-standard way
The Shout has been in Nordic culture before Jurgen Windcaller was born. I find it very weird that the High King of The Nords can't use a Shout
they greybeards, if you talk to them, and Ulfric, who was going to be a greybeard, say that they really abhor the use of the voice for anything other than meditation and prayer, though the greybeards acknowledge the necessity of the dragonborn using it in combat, plus dragonborn is exempt.
But Ulfric had training next to no current nord has, does not seem to have told more than a handful that he was trained in the way of the voice to be a greybeard, and certainly did not inform Torygg. He even says he doubts he'd be welcomed back to High Hrothgar, or that the Greybeards would approve of his use of the voice.
He also says "I challenged him in fair combat. true, he never stood a chance. but that was precisely the point." What was the point? That few can stand a chance against one trained in the Voice? Well duh! I could tell you that, after killing countless via the voice. But how does that prove you're better in combat? You pussied out, Ulfric. You didn't fight man to man, you used a very powerful, hidden magic ability to cripple your opponent, then stabbed him.