Need Help With Writing a Legal Memo on the Word "Offend"

So basically this deals with the transportation of bodily fluids or waste via mail. The law on it says that if you send such materials for the purpose to offend, harass or otherwise harm the recipient, the crime is Assault, Battery, and a whole host of federal crimes once the package crosses state lines.

On the "offend" part I know it deal with for example if a disgruntled person decided to mail a turd (feces) to a person for mean purposes, this is technically illegal, because doing so means you can expose said person and the other people handling the mail to diseases and so forth.

The part that I have to write a legal memo discussing is on the word offend and why it matters, or should not matter, in this case. I honestly have no clue on why offend would matter, I mean I can understand it being illegal for the harm and harass aspect, but on offending them, I am confused.

The thing is, this is my first ever legal memo however, and I have no clue where to start. Are there court cases regarding this issue I can look up to refer to? I have done Googling on the "legal definition" of offend but gotten nothing (just definitions of "offender" and the dictionary definition of offend seems useless).

I know I have to present a balanced argument on this, but I am just so confused, don't know where to begin, please help. I don't know how to argue the aspect that such an act should be illegal because it can offend the recipient (or necessarily why it should be legal either, but from my understanding, you don't have a right to not be offended...?).

Any suggestions welcome, please help (and not asking for anyone to write the thing for me, just need some guidance). The memo can be no longer than 20,000 words, but I am assuming it thus must be detailed and long still (20,000 words double-spaced is 80 pages).