Why did my parents just suddenly get overprotected?

Ok so one day my younger brother and I were watching terminator 3 on our cable tv for like the 20th time or something, then when the movie got to the part where arnold got naked in that biker club, my mom started yelling at me about how i was allowing my brother to see that sort of stuff. i was like " jeez we watched this at least 5 times... and dad watched it with us once! i mean it only shows him naked up to the stomach" but my mom still kept pounding us with stuff -_- then when i came home from school and finished my homework an hour and 15 min or something later, i was watching a star wars/supermive black hole (muse xD) video on youtube when my dad saw me and yelled at me to get off becasue "youtube was messes up your brain and stuff" i have to admit, there some bad stuff on there, but i mean i dont search them. this happened to my brother when a new episode of that new star wars clone wars showed on tv and my mom made him watch something else or else....(i didnt hear what she saID AFTER THAT =/) because it was rated "PG". my brother started crying because it was like his favorite show