Not really that petty. Even if you count it as a piece of junk, that's YOUR piece of junk and you have every right to protect it and feel disrespected if someone stole what was yours.

I think that you feel hurt by it because you feel disrespected... because I think you feel lke it's the principle of the situation and not because of the item itself.

After all, if people see you don't care they took your door mat, next thing is gonna be your flower, then your toaster, then your coffee maker, then your blender, then your car, next thing you know you lost all of your possessions.

So it makes sense you feel upset someone stole your door mat.