By the time it's damaged a wing leading edge or broken a compressor blade, there won't be much of the battery left.
There are "soft" spots on the plane skin. For example you can hit the radome as in this supposedly drone accident from a few days back: https://www.nbcnews.com/nightly-news/video/mexican-authorities-investigating-whether-drone-crashed-into-aeromexico-flight-1398464579774
When a plane is taking off or landing it has most of its mechanization on the wing enabled. This opens lots of lovely hydraulics for a drone to "attend to" in a collision. That is way worse than hitting the wing leading edge or even an engine.
There is also the cabin wind-shield. In fact, the drone strikes may be the final straw which will finally make the "crew looking out of this window" obsolete resulting in the crew being moved to a "secure compartment" and everything switching to cameras in 10-15 years time.
By the way "bullets" is the wrong idea. You either use a missile (as on the anti-drone installations for the World cup this summer) or you use a shotgun mounted on another drone. The shot from a shotgun is relatively harmless at a distance as low as a few 100m and I have yet to see a drone which can sustain shot from a shotgun at point-blank range.