It is a great shame that such an image, expressing ideas contrary to what the Orthodox Church teaches, was painted by someone who is Orthodox, and who has been painting icons for a generation. This isn't the honest mistake of a novice.
If it was painted by a veteran Orthodox iconographer who should know better, why wouldn't s/he know better and do better? Or is there more going on here?
This person is not the only Orthodox painting unsatisfactory images. Most of his work is fine, but the continued presence of this and at least one other of his works in Orthodox bookstores and on his website is cause for concern. If painting these images was indeed an honest mistake, then they should be withdrawn from circulation. If these works were painted for a non-Orthodox patron, then they should be clearly designated as such, and not disseminated as Orthodox icons. There comes a point in an iconographer's life where he must draw the line and decline commissions where the subject matter is contrary to Orthodox teaching, whether the prospective patron is Orthodox or not.
There are plenty of others, including the Andreyevs of the Prosopon School, and Fr Stamatios Skliris, a Greek Orthodox priest. These hold themselves out to be authorities on iconography, yet a good part of their work is unfit for veneration, to put it mildly. The Schlock Icons thread has ample evidence of this.
As to why such "knowledgeable" people continue to paint unsatisfactory images, it doesn't take much thought to come up with reasons why.