I worked on a controversial app. I generally take the letter then throw it into the trash. I did this for 4 years, never had an issue. Github was the only one that seemed to want blood - then banned me. They would send me weird emails, trying to trick me to admit fault. They would also track new accounts I made (ip) and send taunting letters. They gave up eventually too.
Looking back, these companies can send these things out for no cost, looking for you to mess up by replying. If they want to sue you, don't worry, it will happen.
On the NANAE newsgroup, law firms would often pop up threatening legal action against blocklist maintainers or mailadmins; the standard response was "Where is your writ?".
Looking back, these companies can send these things out for no cost, looking for you to mess up by replying. If they want to sue you, don't worry, it will happen.