If you say you have a deep understanding of a subject – say marketing or branding – I would submit to you that you need to have substantial experience, being well-read and researched on the subject. Otherwise, you cannot claim that.
And if you want to argue your points, then debate it intelligently like good scientists do.
Debating intelligently is a critical skill regardless of your field. If you have any respect at all for your profession, you need to up the knowledge in your subject matter, gain experience and synthesize them for your own informed point of view.
How do you debate?