Where in the Constitution does it say that the Bill of Rights is not absolute?

The fact is these rights were crafted to be absolute.  Until early in the 20th century, they were absolute and then things changed. The concept that rights are not absolute, particularly in the context of the Bill of Rights, was famously articulated by Supreme Court Justice Oliver Wendell Holmes, Jr., in the case Schenck v. United States, 249 U.S. 47 (1919). In his opinion, Holmes wrote, “The most stringent protection of free speech would not protect a man in falsely shouting fire in a theatre and causing a panic.” This statement marked one of the earliest and most influential judicial crossroads that this certain right—specifically the First Amendment right to free speech—is not absolute and may have limitations under specific circumstances. The Schenck case was later used extensively to gut the second amendment along with search and seizure and due process rights. 

Weighing public safety and modern times simply became an accepted method that brought on the flawed idea that the Constitution was a living document that could be changed along with the needs of the nation without going through the proper political process. 

It wasn’t until District of Columbia v. Heller, 554 U.S. 570 (2008); McDonald v. City of Chicago, 561 U.S. 742 (2010); and finally New York State Rifle & Pistol Association, Inc. v. Bruen, 597 U.S. ___ (2022) that the current Supreme Court effectively put an end to interest balancing regarding the Second Amendment. 

Now, we must explore other avenues to reverse the effects of interest balancing that have eroded our rights—especially concerning search and seizure and due process protections.  Simply put, modern times or public safety cannot be used as an excuse to take our rights away.  We do have a proper political process that would allow those kind of restrictions.