That is the unconvincing argument for the (extremely) undemocratic Senate. The House is supposed to reflect the will of the people which is why we apportion representatives according to the states' populations; the only compromise was that no state would receive less than one representative.
Really though, appealing the logic used 250 years ago is not very convincing. We have different concerns today than we did in in the 18th century. We are not trying to convince a ragtag group of states to form a union, the union has formed and is unlikely to disintegrate. Today we have a problem of bad representation in Congress, and it has been getting worse and worse with each passing year. It is not just about state borders, it is also a problem of how districts are drawn within states, and a proportional system would address that as well (why should we ever talk about gerrymandering? it is an artificial problem that can easily be solved). Year after year a majority of Americans have watched as people the party they voted against somehow took power, kept power, and received just enough power to prevent widely supported initiatives from going anywhere. The trend has been getting worse and worse as Republicans from sparsely populated states have become more and more aggressive at pressing their structural advantage. That needs to be addressed before people start questioning the value of democracy itself.
