D Louth 77, I personally do not have a problem knowing that you are in the hi-fi retail business. Any more so than if you are a doctor or an accountant. Your (personal) opinions are as valid as anyone else, perhaps more so than most as being in the business, you will have more experience with a wider range of kit that most.
My biggest problem is in dealing with people who decry a concept without actually checking it out for themselves before publishing their opinion on the concept. Likewise I believe it is a fact that certain kit such as mains cables, supports etc. can have a significant effect on the sound of a hi-fi system. It is also true that these same items may have no effect on another hi-fi system. In other words, there are few absolutes in this hobby of ours except our love of music. Therefore users ought not feel constrained to mention any perceived gains from the use of mains cables etc. in case it incurrs the wrath of the non believers on Forums.
I subscribe to a number of Forums, mainly guitar and have received tons of scorn as a result of pointing out that low bitrate MP3 is rubbish sonically. Amazing really as these posters are musicians, most of whom could play me off the planet TBH, but it seems that musicians are the most cynical and least receptive to concepts that don't fit into any technicial or accepted 'box'. Yet these same guys will decry the purchase of a guitar that is painted the 'wrong' colour or has gold plated hardware! Despite the fact that playing wise or sound wise it is identical to a plain black guitar.
So the gist of this post is to express your honestly held opinions and accept any flak. The alternative is to say nothing or equip yourself with a cross section of Forum membership acceptable kit such as valve amps, high efficiency speakers, no name wires etc. etc. Me, I prefer to use my own ears to help decide what kit I listen to and take what is thrown at me.