I agree with that statement, but there isn't a harm in not being to buy something at a store that you want.
Your argument is fatally flawed (and this was pointed out multiple times in previous threads on this topic)
The "harm" is not from a particular store not carrying a product you may want. The harm is from that store discriminating against you by refusing to sell you a product they DO carry.
The "big and tall" store is not required to carry clothing for short people, but they ARE prohibited from refusing to sell the 'big and tall' clothing they DO carry to a particular customer because said customer is gay or black or female or short or whatever.
Likewise, no baker is required to bake wedding cakes for anyone, but if they DO bake wedding cakes for sale, then they can not discriminate against any particular customer by refusing to bake the wedding cake.