I approve of properly tested GM for the right reasons. Resistance to herbicides is not the right reason. Resistance to blight is a great reason.
If you engineer plants to be resistant to herbicides, poor farmers need to buy the herbicides to take advantage of the modification, and herbicides should be avoided as far as possible anyway.
Engineering the plants to resist disease and environmental stressors protects the investment of the farmer and will increase yields without forcing unpalatable and expensive practices on the farmer.