Should I send an angry letter to a company that treated me like shit when I tried applying?
++ the yes or no comment.

I should send it

i should NOT send it

Na just ignore them

@hypervtechnics but.. I'm still thinking about what they've said to me ~2 days later.I let it get to me....

Ignore.

They're not worth your energy, ignore them and move on.

They won't bother and you won't achieve anything. Just ignore them.

It will only satisfy your inner ego, nothing else. Don't fall into their level, you are too cool for that.

It can even affect your future life badly, if somehow your next company would try to contact this company about you.

If possible, look for a different job and leave. If not, try to compensate until you find a decent job.

A good behaviour can cause some change of heart, but bad behaviour will always create more hatred.