Second, I don't believe it's infallible. Men are inherently fallible, and thus anything created by men is as well.
With that said, I do believe as a foundational governmental structure and philosophy it's the best that I've personally reveiwed or studied. It was created by men whom I believe to be exceedingly intelligent, through a lengthy and detailed process, with great research and thought put into it during a time period where the context surrounding it was of utmost importance to it's formation and philosophy.
I view it as I do many comprehensive items, be it in politics or elsewhere, in that it functions best when it's entire system is respected and utilized rather than attempting to tinker with a part here or there without a significant and meaningful understanding of how the various portions interact together to form a cohesive unit.
I believe that it's a well crafted document with an necessary firmly formed foundation that has an incredibly flexable house built upon it. However, that flexability is not always easy to attain and I think that's actually a GOOD attribute of it...but for many, because it's difficult (and maybe even impossible for their ends) then they instead seek other means to reach their ends, such as tearing down that which doesn't allow them to do what they want.
I don't believe it's infallible, but I think it's a great foundation and something that I'd rather see the country adhere to than not. There are a MULTITUDE of countries all around the world that have varying political philosophies. I enjoy the notion of CHOICE (ironically enough how that word works in various debates)...I don't want to see the United State's, and the foundation of it's political makeup (IE The Constitution), simply become marginalized as just another European-style western nation because a few people who are upset that the "means" to their "ends" are too difficult under the american mentality of government. I like having a CHOICE of a country whose founding principles and governmental foundation is one where the people bestow power upon the government, not the other way around. Where the government is a servent, not the other way around. Where limited governmental intervention is preferred over additional. Where the freedom to fail or succeed is present, rather than an attempt to artificially create a level society. Is that the BEST method? Who knows, that's a question of personal preference. But it's at least a somewhat unique method, which institutes a notion of CHOICE and an ability to try a different way.
Instead, you have people who are upset that they can't have their cake and eat it too...that they can't reach their ends in America, so they try and forcefully change the means and remove that CHOICE from people. That their own personal "ends" are the ones that must be followed to the highest political points possible and to hell with the rules, traditions, laws, or foundational guidelines.
I believe that the United States Constitution is absolutely fallible; it is of man. But I do believe it's the best foundational basis that I've seen for a country, and that it should be adhered to as best as possible in line with original intent and within it's framework and that many of the problems and pitfalls identified within the Constitution largely form due to attempts of distorting, contorting, and outright wrongfully reworking that framework into a frankenstein of what it was creating a flaw within a system due to ignorance and ego of those seeking their political ends by any means necessary. I believe that if someone comes forth with an actual foundational governmental system that I believe is better that I would fully and completely support it despite it too being fallible...but until such time, I will stick with the one the one I believe works best.
EVERY system made by man is fallible. Highlighting that the Constitution is such is like pointing out the sky is blue and then laughing as if that won you an argument. ANY change or alteration that is sought to be made to it is ALSO fallible. The real question is....do people have greater faith in the thought processes, intent, motives, forethought, intelligence, and research done by those at the time of the founding than they do with regards to Joe Jackass Activist or Bleeding Heart Barbara or every random Internet Pseudointellectual political hipster?
My answer would be yes, yes I do. And without seeing a significantly presented, reasoned, and thoroughly backed up argument as to why the Constitution should be scrapped entirely, or why a particular portion or philosophy of it should be scrapped, that actually does a great job of showing why the replacement would be better or the change wouldn't damage the system as a whole then you're unlikely to find me rallying behind some effort to "fundamentally transform" it.