This is a good point. Before things get silly you may want to consider that there may not actually be any trademark infringement by simply using a brand name to describe what Amp you actually profiled during the process.
My understanding is that a trademark is an indicator of origin and there is only an infringement if your use of the mark causes a consumer to think that what you are selling is made by the owner of said trademark, or causes confusion that the product may originate from that owner.
In my opinion (and this isn't legal advice) by simply describing the fact that you used say, a Fender Amp to create a profile, doesn't infringe a trademark.
To take an extreme example. If you ask the Edge what he used to make the last U2 record and he lists his gear somewhere - he is probably not going to be done for trademark infringement. He is simply describing the equipment he used.
You guys have effectively created a type of EQ or impulse response using a particular Amp. You are simply describing the amp used to create that. So long as you make it clear that the Amp company name is only to describe the equipment you used to create the profile I don't see how that can cause someone to think that the product (the profile) actually originated from that company.
Now it is all very well me saying this, but in practice it is pretty scary having a big company threaten you legally I am sure. They may have a legal leg to stand on - but they are probably just trying to scare you. They can't be happy about the Kemper as a product after all.
I am based in the UK and I am pretty confident that this isn't trademark infringement over here. But that is my opinion - not legal advice at all. I think it would be wise for any commercial profiler to seek independent legal advice before deciding how to go ahead with a strategy - the law may differ in other countries. There is also some useful stuff available in the public domain. You can check the WIPO site for example.