this makes more sense if the bb spindle wasn't greased before installation, and if the crank arm was drastically overtightened... but still... stripping out all of the threads from a new crankarm from a reputable company seems a bit unlikely without some other factors involved. crank pullers are some of the easiest tools to use. not ragging on you man, but this is just an unlikely thing to happen if you're doing things right.

there are obviously defective parts here and there as well. sorry to hear about this.