Sauron is arguably the protagonist

Firstly, I have to point out that a protagonist is the main character of a story.
It is not about whether this person is good or bad.
Yeah, it is the most common thing traditionally that the protagonist is (supposedly) likable and often even heroic.
But still, there are stories with villain protagonists out there.
Rather, you have to find out which character's point of view is the most important.
It is that character, who is the protagonist even if he or she is evil.
Thus, it is clear that Sauron can't be a protagonist even if you would sympathize with him.
He is the antagonist, which is the character who is in opposition to the protagonists.

Well, it is not like industrialisation only is a good thing.
It is implied even within these movies that deforestation is destroying the environment.
It is made clear also that what Sauron and Saruman are doing is hurtful to most creatures in their world.
And seriously, it is not like they think about ending absolute monarchies or fighting diseases at all.
No, they are thinking about nothing but getting power for themselves.

OH, STFU!!