I agree. I subscribed to National Geographic for my wife for at least 15 years. I noticed the slant at least 10 years ago. It got worse and worse till I gave up on it 5 years ago. Kept the subscription for my wife. She let me know last year not to renew as she had reached her breaking point. She is far less political than I. That they managed to run her off speaks volumes.
If you examine the fact that its a not-for-profit organization...then the number of subscribers really don't matter. They've been able to develop their TV operations and their on-line store to help make up for magazine losses. They certainly won't admit that they've lost 10-20 percent of their magazine sales...but it doesn't matter. Corporation advertsing on the tv network carry the entire organization.