I'm quite shocked by some of the comments on this thread. Bloody hell.
To answer GrandadOnagar's repeated calls for Jews to kill each other over religious differences; in answer to your question, no, you do not kill another person if you disagree with them. It is repeatedly stressed in the Talmud that there may be multiple answers to the same question, all right, because people are taking it from a different viewpoint. If there is a major dispute, you could take it to the Beth Din and they would make a final ruling.
As to whether or not walking past a motion activated light breaks the Shabbos rules; you would probably get fifty different answers to whether or not it is. And to be honest, I don't think that leaving a light on for 52 days a year is going to greatly contribute to global warming. And, on balance, they would not be using other electronic equipment such as cars, radios, computers, TVs, washing machines etc. for the duration of shabbat so that more than balances it out. Finally, the light would not have to be left on all weekend, just over the 25 hours of shabbat (from Friday evening to Saturday evening).
but again, I am pretty shocked by all the anti-religious and anti-Jewish vitriol on this thread. (though am quite impressed with MorningPaper)