Many traits have genetic and environmental causes. Hence the age - old nature/nurture argument. Most biologists today recognize that both genetics and environment are important. Besides, even if it is ALL environment, that still doesn't make it a choice. The best argument in my mind against it being a choice is why would anyone choose a behavior that in most societies is going to get them taunted, scorned, beaten up and in some cases killed, with very little if any benefit over the opposite "choice"? That is, all they are getting for their choice is sexual gratification. They could get that by making the opposite choice and be accepted by society.
Besides, I wouldn't trust Dobson on anything having to do with science and human behavior. He is perfectly willing to "lie for Jesus" when it is convenient, regardless of the consequences Anybody that would promote "gay conversions" and subject women to the tragedy of being married to a man who isn't sexually attracted to them is fundamentally dishonest and not to be trusted.