If your neighbour can also get symmetrical internet with a residential contract, then that would be the better example to prove his point wrong.
A business contract is not a good comparison because they usually are symmetrical for a premium price regardless of the quality of the residential internet in your area.
Even in my country you can get symmetrical internet with a business contract, yet I'll never claim my country's internet is comparable to one that do provide it for a normal residential connection, because we don't have that option here.
And he did say his internet was a normal domestic internet, btw.
You're not making a good look for your stance when you over hyperbolize the situation.
I needed to hyperbolize the situation because you can't seem to grasp why a business line wasn't a good comparison, as you can see from how it works in my country. All you needed to do was provide the point that the symmetrical internet is not exclusive to a business contract and it would have made your argument completely valid.