From what I'm getting, this is in regards to a product that was reviewed that has a similar appearance to an LRI product?
Companies and their lawyers send out nasty letters all the time. More often than not there is no legal ground for them to stand on, and they know it. It's just intimidation. Most of the time they can't do anything but send more nasty, empty-threat letters. Until you actually get papers from a court, it's all hot air.
Getting the lawyers involved may also imply that they LACK (or have very serious doubts about) the legal grounds for the request.
Seems to me, especially if you're doing a review and the review is your own personal opinion, there shouldn't be much they could do about it. You're not advertising the product, you're providing educational information for anyone who looks at your website. You didn't make the product, you don't sell the product, and all you provide is free information about the product. Their legal beef is with anyone who makes money from the product.
Of course, receiving revenue from the site could be your Achilles Heel - Technically you are making money from your review of the product (by attracting visitors who then see your advertising), even if it is not from the product itself.
Personally, if the company owner contacted me directly and asked politely to have the offending review removed, I wouldn't have a problem with it unless it was for purely selfish reasons. You catch more flies with honey than with vinegar.