Difficult question.
The constitution is our founding document, and for that reason alone it should be respected to some degree. However, yes, it WAS created in the 18th century and the world has truly changed since then. I do believe that the system in place for ratifying a new amendment is a bit antiquated, I would even go further to say our entire delegate process is antiquated, but I digress.
The reason why this question is so tricky is because it lacks any type of nuance. This question ultimately puts people in two camps, and any question that does this is a no no in my book.
Do I believe the constitution holds some unique truths and foundations for a civilized society?
Yes. The bill or rights alone is something that shook the entire world to it's core. It was uniquely different from what was going on in Europe at the same time. In Europe you saw constitutions arising as well, but they were usually centered around the benefits to a group of people, to society at large, to the collective. Our founding document was centered solely around the individual, and this is the single biggest reason that it needs to receive a high level of respect. Now, respect doesn't mean you can't want to change it. You can respect your 80 year old grandfather, but when he's pinching the butt of the waitress at IHOP, something's gotta give.
Do I believe the constitution is infallible and shouldn't be changed ever? No, and the majority of libertarians would agree. Like you said in your video, there is an amendment process. I do believe it is extremely antiquated, and I think we should have a much more direct way to amend the constitution. This goes hand in hand with my longing for a direct democracy through technology, like the block chain. However, it still should never be a "mob rule". We are a republic for a reason, and each citizen in each state has a say in their state, and then those states to the great whole. If we were to go the way of "mob rule", then the people in rural America would always lose, and that's not the way a democracy works.
Anyway, tough topic to tackle, but necessary either way.