I think the kind of impact your friends comment has is somewhat dependent on your experience level, exposure to other systems, and depth of knowledge. For instance if someone said that of my system, I would have to exert some self control not to start laughing. I have been an avid audiophile for fifty years. While I am open to learning, I know exactly what attributes my system has; relative to real music and other systems.
On the other hand, I would become very interested in understanding where they are coming from. I would want to hear what they have been hearing to better understand.
I do understand your reaction. I think it is pretty normal… I’m assuming you have not been an audiophile for fifty years. It would spur me on to understand more. I would certainly want to hear what he is listening to, I would also go out and find some audio stores and listen to what they have. Is there any truth in the claim? If not, great, you can go back to enjoying your system. But if there is… then you can learn something… this is how we learn over time and zero in on what you will ultimately appreciate as you mature.
I would look at your friends comments as a great opportunity to learn and experience more systems.