Why Are Minhagim Important?

There's nothing like Pesach for causing perplexity and wars about minhagim - customs. Recently I was disappointed to hear a reasonably well-educated person effectively stating that minhagim are not important and can be freely abolished. In fact, while there is inevitable debate about precisely how important minhagim are, and what exactly is defined as a minhag, and the parameters of their applicability, there is no doubt that minhag is of great importance in Judaism. But why? Prof. Daniel Sperber, in volume three of Minhagei Yisrael, cites three reasons that are given (I'm writing from memory here, so I could be mistaken):

1) Stability. It's important to maintain established practice, so as to maintain stability in Judaism and avoid anarchy. (In times of turbulence, opinions will differ as to whether stability is better maintained by being more rigid, or by being more flexible. I think that reasonable people can understand that both viewpoints are reasonable.)

2) Preventing disputes. If everyone follows custom, this should prevent disputes. (Unfortunately in practice, this sometimes seem to have the opposite effect. However, this is more a result of the modern era, in which the ease of travel enables people from different communities to be lumped together with great frequency.)

3) Finally, Rav Kook states that since minhagim result from people desiring to demonstrate their passion for Judaism, they must accordingly be treated with great respect. (This would appear to apply to only certain types of minhagim.)

I think that before evaluating whether a given minhag should be maintained or not, it's important to understand exactly why minhag has an important place in Judaism.