According to this Movember advertisement, David's Big Problem is that he's creepy, not that he has a creepy mustache.
This hilarious extended ad is a product of Movember and Sons to encourage donations. In the video, David sports a creepy mustache and opens by explaining "people have been looking at me differently." He picks up an errand soccer ball to hand back to a kid in a park, who looks at him apprehensively. Later, he shows us his day-to-day life and tries to convince us there is nothing odd about him at all. David doesn't understand why people are looking at him this way.
The irony, of course, is that David does look odd -- and creepy. The video ends by saying "A moustache doesn't make you creepy. Being creepy makes you creepy."
Donate at Movember.com