So there are two aspects you must consider when thinking about the Constitution. The first is the literal Constitution and the words in it, the second is how it has been interpreted.
The US Constitution is often shown off to the rest of the world as the ideal foundations of a good democratic government. It puts limitations on what it can and cannot do, giving people rights. Some of these rights specifically mentioned in the Constitution seem a little odd today (the 4th amendment comes to mind, not saying it's bad by any means, but compared with many of the other amendments feels a bit odd.) but come from specific problems that British colonists in what would become the United States faced under British rule. One could see the rights protected under the original Constitution almost as a laundry list of problems the founding fathers had with the British government's rule.
While most of the Constitution has remained the same with just some additions (save the 18th amendment which was added and then repelled) how it has been interpreted by the Supreme Court has changed. Sometimes the courts have directly contradictory rulings when enough time has past. Because these are more subject to change, it is more common to find a person who disagrees with a court ruling (and by extension, an interpretation of the Constitution) than the literal wording of the Constitution itself. For example; Citizens United v. FEC and District of Columbia v. Heller are ones that people on the left are more likely to disagree with, while Roe v. Wade and Obergefell v. Hodges are ones people on the right are more likely to disagree with.
One of the things about the Constitution (for better or worse) is that the wording is often vague, which does leave things open to interpretation. One could say that it leaves "wiggle room" for cases that are complicated, others would say that interpretations that deviate from the strictest interpretations of what the words meant at the time of the writing and what was most likely intended by the authors are wrong. Of course, the people who wrote the Constitution themselves often disagreed with each other on what specific parts of the Constitution meant.
So as for the fundamental question. While questioning interpretations of the Constitution in theory (as opposed to being someone who is breaking the the law because they just don't like what the Supreme Court has ruled) is generally fine. But questioning it in terms of certain bits of it should be gotten rid of, especially parts that were in the original Constitution is much less popular. Removing these limitations of the government to many is seen as tantamount to saying you want the government to no longer have a limitation to not do this, and to be able to do it however it sees fit.
