straight from the MPAA's website
"A PG-13 rating is a sterner warning by the Rating Board to parents to determine whether their children under age 13 should view the motion picture, as some material might not be suited for them. A PG-13 motion picture may go beyond the PG rating in theme, violence, nudity, sensuality, language, adult activities or other elements, but does not reach the restricted R category. The theme of the motion picture by itself will not result in a rating greater than PG-13, although depictions of activities related to a mature theme may result in a restricted rating for the motion picture. Any drug use will initially require at least a PG-13 rating. More than brief nudity will require at least a PG-13 rating, but such nudity in a PG-13 rated motion picture generally will not be sexually oriented. There may be depictions of violence in a PG-13 movie, but generally not both realistic and extreme or persistent violence. A motion picture’s single use of one of the harsher sexually-derived words, though only as an expletive, initially requires at least a PG-13 rating. More than one such expletive requires an R rating, as must even one of those words used in a sexual context. The Rating Board nevertheless may rate such a motion picture PG-13 if, based on a special vote by a two-thirds majority, the Raters feel that most American parents would believe that a PG-13 rating is appropriate because of the context or manner in which the words are used or because the use of those words in the motion picture is inconspicuous."

no mention at all of guardian/parent required.

see for yourself : http://www.mpaa.org/FlmRat_Ratings.asp

and they follow my theory too,  single use=pg-13,  multiple uses=R



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Ive Eaten From The Insane Root That Imprisons Reason

so it falls on where you as a parent draw the line.  

where a single slipup ala'  sundays match i could understand for a child under 13.
whereas your two scenarios are not something a child under 13 should witness
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Ive Eaten From The Insane Root That Imprisons Reason

Earmuffs.
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"Nobody in the game of football should be called a genius. A genius is somebody like Norman Einstein."

-Broadcasting Extraordinaire and Mensa Member Joe Theismann

To all of the parents:

You should hear what your kids say when you're not around.  
The end.
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-DJ Marshall
...The Twelve In a Row Pro Shop.  AMF Bowie Lanes -- Bowie, MD