Recently had a client stiff us for $75k. His lawyer then sent us a letter trying to get us to agree to just keeping the $25k deposit or he would sue us for $1MM

Recently had a client stiff us for $75k. His lawyer then sent us a letter trying to get us to agree to just keeping the $25k deposit or he would sue us for $1MM. he also made fun of my outdated linked in profile and accused me of fraud by restating everything in my CV as "alleged". I spoke with a few lawyers and they said the appropriate response to that embarrassing letter is to throw it away and not think of it again. They never sued for $1MM and technically I have something like 6 years to sue him for breech and the $75k if I want to... Likely won't as the legal bill will be $100k.