Problems with the Wiccan Rede
I have three major problems with the Rede.
First, the Rede is what I call "Sound Bite Morality" -- an attempt to condense a complete moral system into a short, catchy phrase. This has great value as a teaching tool. Unfortunately, every time the catchy phrase "catches on" people soon seem to forget that it isn't the complete moral system.
Take a look at the best known (in the Western World) example of Sound Bite Morality, the Golden Rule ("Do unto others as you would have them do unto you.") In general, this is a good moral principle. It is only when you look at specific cases that it breaks down. For example, Joe Doe really likes to french kiss. In fact, he would really like it if everyone he met french kissed him. So strictly following the Golden Rule, Joe french kisses everyone he meets. The Golden Rule, as you are probably now noticing, says absolutely nothing about respecting the needs/desires of others. It assumes that their needs/desires are the same as yours. An "improved" version of the Golden Rule has been proposed, "Do unto others as they would have you do unto them." While this disallows french kissing those who don't wish it, it goes to the opposite extreme and says nothing about the needs of the person performing the action.
The Rede has a similar problem. It's short and simple -- and it provides good, general guidance in most everyday situations. However, it quickly breaks down in less common situations, especially as interpreted by most of the Wiccans I encounter today. Most seem to think that any action which might cause harm is not permitted. For example, if a Rede-literalist came across a person unconscious and dying of heart failure at the side of the road, they'd have to walk on by rather than give CPR, because they are unable to get the person's permission to help them -- and for all they know the person might want to die (or so they often claim to excuse their inaction).
Many of the Rede's problems in this area would lessen if more Wiccans realized that choosing not to act is itself an action -- and under the Rede not-acting cannot be selected if doing so would cause harm. In the example above, walking on by (that is, choosing not to act) would cause harm and therefore would not be an acceptable action under the Rede. This, of course, sets up a conflict as both helping the person and not helping the person in the situation described might cause harm and therefore violate the Rede. This points out the Rede's biggest problem when used as a complete moral system. It basically tries to force actions into an idealistic world where they either harm or do not harm. The real world is far more complex. Most actions both cause harm and prevent harm in ways that can't easily be separated. The Rede as interpreted by most Wiccans I know today, looks at the individual actions independently instead of at the result overall.
My second problem with the Rede is one of the few moral systems that is truly anti-family and anti-society. No, it is not anti-family/anti-society because it doesn't require one to oppose abortion, same-sex marriages, and all the other nonsense that the radical right in America thinks of as "family/society values." The Rede is anti-family/anti-society because it (as interpreted by most Wiccans I know) forbids one from meeting force with force to defend one's society and family from attackers when one has no other workable choice available. Sometimes one can indeed simply shield and defend, but other times the only choice that allows one's family or society to a real chance to survive is to go on the offensive and cause harm to others.
My third problem isn't so much with the Rede itself as it is the "rhetoric" many Wiccans use in explaining it. Supposedly the Rede is an example of how Wicca teaches self-responsibility. This boggles my admittedly small mind. Self-responsibility is accepting the responsibility for one's actions whether ones actions help or harm. However, in order to have responsibility for an action, one must choose to take the action (which means one must have choices to select between). Literally following the Rede gives one a nice cop-out for one's actions. "Gee, I'm sorry your mother died. I'll have sent her some healing energy, but I couldn't as I didn't have her permission to help her." As one never had to actually choose to help or not to help, the Rede in this situation becomes a way to avoid responsibility (although those following it seldom see it in this light). Unfortunately, I see it being used this way far too often.
A fourth and lesser problem is the one Elspeth pointed out, good advice has been elevated to the status of an absolute law. As I pointed out above, I think it does very poorly as absolute law.
Each of the three major points above could be an long essay in itself (to answer all the counter-arguments I've seen over the years), but I hope this short post at least helps you understand why I have chosen not to follow the Wiccan Rede.
However, please don't get the opinion that I think the Rede is something terrible that should be tossed on the ash heap of moral history. Like the Golden Rule, the Rede is a very good set of "training wheels" for one trying to develop a personal morality based on the Law of Returns (often called the Law of Three in Wicca). If the beginning moral student remembers the Rede as he or she makes everyday moral decisions, the student is much less likely to make a bad decision while he/she is learning to make moral decisions based on the Law of Returns. As a crutch/set of training wheels/broad first order moral filter, the Rede (or the Golden Rule, for that matter) is fine for most common situations, but sooner of later the student is going to encounter situations where the Rede gives bad moral advice. Students need to be taught to grow their moral sense beyond the simplistic Rede and truly make their own decisions based on the Law of Returns. Like a crutch or training wheels, one has to eventually quit depending on it to grow -- and generally the sooner one learns to do so, the better.