Why would a bike rack on a parked car be unsafe?

I have a bike rack affixed to the trunk of my car. It is similar to this. And I live in an apartment complex with shared parking. (Spaces aren’t assigned; there are plenty to go around.)

One of my neighbors left a note this morning warning me that IF I WANT TO PARK HERE I SHOULD TAKE THE BIKE RACK OFF BECAUSE SOMEONE COULD GET HURT!!!!!!

What could that person possibly mean? What dangers do a bike rack on a parked car pose? Am I under a neighborly obligation to accede to this request?