I think I understand where he's at. If your web site has compatibility issues with smaller browsers like Firefox at 3%, Opera at 2% etc. then you could be losing out on 5% of your sales. If you were to approach any CEO and ask if they'd be interested in an initiative to increase sales by 5%, they would most likely express an interest.

IE6 was already announced dead by Microsoft when it reached so tiny market share, you are forgetting IE got several versions up to 11, before being replaced by Edge, followed by Edge Chrome, later rebranded as Edge.