I’ve never understood the censoring of lines about guns for US radio airplay. You can play “Janie’s Got a Gun” by Aerosmith, or “Barrel of a Gun” by Depeche Mode, or plenty of other songs that mention firearms with no cuts. But if you’ve got something like your friend’s song, or “Teenage Dirtbag” by Wheatus, one mention of the word “gun” gets censored. What is up with that?
Pfft. Two years ago, I saw somebody on MTV reading from the [Ken, not Ringo] Starr Report - discussing what Bill Clinton did with that famous cigar. The network bleeped the word “inserted.” I’d say you’re at least a few years late. 
Also still played commonly without editing:
Pigs by Pink Floyd. “You fucked up old hag…”
FM by Steely Dan. “…fucked up muzak…”
Man in the Box by Alice in Chains. “Shove my nose in shit” gets played here either unedited or editied, depending upon station and time of day.
I can find no reference to that being one of the lyrics on the Internet, but I could be wrong- after all, there are radio edits for other songs (You’re Beautiful by James Blunt, for example- “flying high” replaces “fucking high.”) But the strangest thing about that song is that some radio stations edit out the first verse, so the song starts with “I don’t got digital…” Are the radio stations run by Communists?
Steely Dan’s Show Business Kids seldom gets an edit despite the line: “Show business kids making movies of themself you know they don’t give a fuck about anybody else” and I’ve heard Jefferson Airplane Volunteers run with the line “Up against the wall, motherfuckers” many a time. Perhaps it’s just that these songs are so old, culturally speaking, that the naughty language goes unnoticed.
In the past they edited out stuff on radio that wasn’t even four letter words. The Stones" Let’s Spend the Night Together" got changed to “Let’s Spend Some Time Together.”
I didn’t know, either. I thought it was either “passing the night away” or “kissing the night away.” This is probably one of those songs that slips by because no one understands what the singer is trying to say.
And what does that line mean, anyway? I’ve heard the British use the word “pissed” to mean drunk. In America, “piss” means to urinate. Depending on which meaning is intended, that line can be interpreted in two very different ways 
I thought that was only when the Stones appeared on Ed Sullivan. I never heard about a radio edit of the song.
Ed Sullivan made them change the words when they appeared on his show. The song wasn’t changed for radio that I know of.
Sullivan required lots of groups to change or censor their words. He banned the Doors from ever again appearing on his show when Jim Morrison went ahead and sang “we couldn’t get no higher” despite promising that he wouldn’t.
But that was almost 40 years ago. And it was live television, not radio.
“Piss” can also mean to waste which, in the context of the song, would also work (i.e., wasting “the night away”).
Has to be. ‘Urinating’ the night away away don’t make much sense.
In the context of the song, they’re pissing the night away, by pissing it up.
The simple answer is that “piss” just isn’t that severe of a profanity. TV shows routinely use it and “ass,” and it’s no big deal. The FCC mainly goes after “fuck” and words of that ilk. Even then, their enforcement is uneven.
I take a whisky drink, I take a vodka drink
And when I have to pee, I use the kitchen sink
I sing the songs that remind me I’m a urinatin’ guy
-H.J. Simpson