It could be phrased differently still without insinuating that what they say is worthless. Something like, "How will you back up your claim of the product not

It could be phrased differently still without insinuating that what they say is worthless. Something like, "How will you back up your claim of the product not being discontinued?" or "What will prevent your product from being discontinued?" Gets the same point across without coming off rude (it may just be me but saying "your claim ... is worthless" seems rude.) The OP of the comment definitely has a good point but it's said in a way that isn't constructive.