I would like to send a cease and desist letter on defamation. I already created a template. Why would I want this to go through an attorney? If so,

Because you have no idea what you are actually saying or doing from a legal perspective and because an claimed victim letter saying "stop it!..." will usually be laughable to the claimed offender, or worse make threats that you can't or wont back up like "if you don't stop the conduct I will hire a lawyer and sue you! and for punitive damages and everything you own!!!!!...!!!!" I can't tell you how many defamation consults I have had where they intimate legal action AND THEN when whey realize the cost and that lawyer wont take defamation cases on a coningent fee, are left looking impotent and stupid which often emboldens the other party to ramp up the issues even more.