Self-Appointed Experts...

...should not try to give up unsolicited advice. I went to the chemist's to buy an ice pack as having some knee & ankle trouble. Saturday employee "advises" me that I should go and see the doctor, so I ask why - I know what trouble is, I know remedy - I just want something more durable than a bag of frozen peas, if problem desn't go away I'll ask to be referred for physiotherapy. After all I've lived with intermittent knee trouble for many years and have always been advised to follow this course of action. This is a bit like the annoying dad "You don't want to do it like that, do it like this".
Had similar epic in Halford's trying to convince them of fault in car CD, they have now agreed that the unit has a fault and have sent it away for repair - why couldn't they believe me first time, after all the customer is always right? Isn't he/she/[insert gender specific pronoun of choice]?
more to the point why don't these self-appointed experts every get severely injured for their unwarranted information giving - if I want advice I'll ask for it, if I don't I get severely irritated...just follow the trail of headless shop assistants to find where I'll be hiding...