Nowhere did I say "not" to make a pair. I said it would be advisable to "create" your pair using fish from different sources to hopefully create a stronger bloodline "if" you plan to breed them.
When you see several juvenile clowns in a tank at the LFS you can be assured they were captive bred and are all from the same "batch". You cannot be assured how strong the specimens will be due to the possibility of inbreeding. With this being possible it would be wise to try and mix up the bloodlines of any "pairs" you attempt to make. Check to see if your LFS (if you can trust what they tell you) can order wild caught or F1 clowns for you, they will be a bit more expensive. As I said above, inbreeding does not generally cause as much damage in fish as it does in mammals but why do it if you have a choice?