While there are many giants in the Faerie Queene, you definitely remember this particular giant in Book 5 who tries to convince a massive crowd of people that earth and land are unfairly balanced. Essentially, this giant represents the threat of egalitarian equality and views that in our time would be essentially equivalent to communism or socialism. This giant wants everyone to be equal, and in a hierarchical, aristocratic monarchy where a very small handful of people control lots of things, this is not a good thing.
By making the giant want to claim something so unnatural as to make the amount of land and sea equal, Spenser is trying to make the giant's claims about equality between people sound extra bizarre and also unnatural. Artegall, who faces the giant, responds that inequality among people is the natural state of things and that's therefore how things need to remain.
Even though this giant is pretty different than other giants we come across (who are often tyrants or enslaved by lust), he is similar because, like them, he seeks to violate what Spenser considered to be the natural order of things. Whatever you might think about this issue, in Spenser's universe, the natural order is the right order… and the natural order was inequality.