The idea of the "Grammar Nazi" is a flawed one on it's face.

While using standardized English is a helpful tool to understanding, some people, normally ones with decent, but not outstanding, intelligence try to control the flow of ideas using the only tool they have.

Their education.

Now, on the surface this would be fine, if they were arguing facts that were important to the topic at hand. Instead, since that's often not available to them, they seek to control others using what they can scrape up.

perceived flaws in written language.

Notice that I say "perceived"?

That's because language is actually correct, if it's understandable. The purpose of language is to communicate idea's, so as long as the reader can understand what is written, it is, by definition, correct.

That idea bugs the heck out of some people, who were schooled to believe that only the way they were taught in the fifth grade counts.

Languages that are living are subject to rabid change. It's uncomfortable for some, but it is, in the end, the face of the matter.

Don't worry about the Grammar police, they have no power and don't understand the topic they claim to be teaching you. If they did, most often, they'd keep their mouths firmly closed and walk away.