What did he think he was buying ? It wasnt branded Wisper even if it looks like one so why did he buy it? Are they cheaper than Wisper's ?If so it looks like he was trying to have his cake and eat it.Tough .His gripe is from when he bought it and nothing to do with Wisper .There's crap copy products on sale of every thing ,not just ebikes .If I bought a shoddy pair of trainers I'd take them back to the shop and ask for refund as theyre not fit for purpose.It wouldnt put me off trainers for life ! Dont give too much time to this guy,move on imho.I'd make sure that the Wisper and your dealers say some thing like " If it doesnt say Wisper on the frame then its not a Wisper " and " Whilst immitation is flattering ,it can leave you with an expensive mistake " or similar
Get your lawyers to get them to remove all traces of your name and references to Wisper from their site.If not you could look for loss of earnings.The look of the bike you can do little about as discussed in previous thread on the same topic