This is disingenuous. A letter sent by a law firm "to outline our legal concerns" which uses legal language and tells a site that they will settle matters amicably if they meet a demand is a legal threat. It may not actually include the words "or we will sue you", but trying to spin it as not being a legal threat is absurd.
Any communication, however artfully phrased to be non-threatening, from an attorney or a corporation can be taken that way. However, the option of not communicating is not viable.
Fred Bauder