"I hated them for they were so phony" is that correct English? I heard it from Kurt Cobain

Yes, "for" is functioning like "because"

It's correct but it sounds a little stiff to my American ears. I am mainly used to seeing "for" in that context in the King James Version of the bible. Everyone would understand that fine but I think people around here would be more likely to say "I hated them because they were so phony."

Yes, but the use of "for" as a synonym for because is somewhat formal and somewhat old-fashioned. The opposite of Cobain's image.

Important context: This line is not from usual English, it is from a spoken word poem, [Aberdeen](https://en.wikipedia.org/wiki/Montage_of_Heck:_The_Home_Recordings). I expect Kurt wrote this in around 1986-1988 when he was around 19 years old, when Nirvana was just forming, before they recorded their first album *Bleach*, the predecessor to *Nevermind.* It was recorded on a consumer cassette recorder and released decades later on a posthumous record called "Montage of Heck: The Home Recordings," which shared just one of about 100 tapes Kurt had recorded in those years, and never intended to distribute to anyone. I think Kurt is stylistically drawing on the work of Beat poets from the 1950s, especially Allen Ginsberg's work like [Howl](https://www.poetryfoundation.org/poems/49303/howl), and Modernist writers like James Joyce and books like [Ulysses](https://www.gutenberg.org/files/4300/4300-h/4300-h.htm), both of which draw on older forms of modern English going back through the past 400 or so years. It's correct English, but not how he or anyone else talks in normal conversation.

It may be correct but still sounds awful.

Sounds really strange. I can’t imagine kurt cobain speaking this way…was it a song lyric?

"For" can sometimes be used as a conjunction, in this case comparably meaning "because." It's very formal. I wouldn't be surprised if he spoke like that to appear more literary. It should be written with a comma for better cadence: "I hated them, for they were so phony."

Sounds like a french would have translated it literally. " Je les ai haïs pour avoir été si faux."

I didn't see the original quote, but I wouldn't be surprised if he paused and changed direction mid-sentence. Like "I hated them for... (changes topic slightly) they were so phony."

To answer your question, yes, it’s grammatically correct. To add to your question, I’m almost certain that was just a [slip of the tongue](https://www.collinsdictionary.com/us/dictionary/english/slip-of-the-tongue#:~:text=If%20you%20describe%20something%20you,a%20slip%20of%20the%20tongue) by Kurt Cobain (if it occurred in an interview or conversation, and not in song lyrics). He probably meant to say, “for being so phony” or “because they were so phony,” and both messages got mixed up in his mind, so what came out of his mouth was kind of a mixture of both. Happens all the time: “Shut out the lights” and “hit the lights” blend together sometimes into “shit the lights” by accident.

A bit archaic but correct.

Like others say, it’s correct but old/poetic. There’s a famous quote about Alexander the Great which uses the same phrasing: “Alexander looked at the breadth of his domain and he wept, for there were no more worlds to conquer” (sometimes shortened to just “Alexander wept, for…”)

To expand on what others said, “for” meaning “because” sounds antiquated, while the word “phony” is newfangled.

It’s correct but a bit poetic and outdated-sounding to use “for” instead of “because.”