I've Been Told I Have A Serious Problem

I received an email tonight in response to a couple different google ads I have placed for my Passport-related web site. Here's the main thrust of the email.

"Integrity is not leaching
off somebody elses
business by linking to their site with why would a
diamond quit.That is LOW Life
and not respectable at all.
I would highly
recommend you removing them or you
may create a serious problem for
yourself,"

I must say that I appreciate this individuals concern for my future and, I assume, safety. I only wish they would have included their real name or email address so I could thank them properly. I am trying to imagine what imminent "serious problem" to which they could possibly be referring.

As they speak of my questionable integrity, I suppose emailing a veiled threat is acceptable in their book. How much integrity is required in the "leaching off somebody elses" hard earned money by promoting a deceptive marketing plan where less than .0003% of the participants succeed? Is it respectable at all to conceal a profit center within what is labeled a "training system" that produces far greater income for the elite within that business?