Stare decisis is a serious problem. It pretty much means, "No matter how bad, immoral, unconstitutional, destructive, or stupid the ruling was, it was made by nine philosopher kings in black robes, so we have to abide by it for eternity".
Just until its overturned by a new SCOTUS or by constitutional amendment. Stare decisis gives consistancy and stability to law. Very, very important.
As for Marbury vs. Madision who else but the SCOTUS is to decide whether Congressional Legislation confirms to the Constitutional mandates? It's part of checks and balances. The way to change the Court's decisions is by changing its members.
Oh I don't know. It wasn't a problem with the Lawrence decision.
Unless it advances the liberal agenda, then it can be overturned without much thought of course. Even if it was decided just the opposite by essentially the same justices 17 years prior. See Bowers v. Hardwick (1986) overturned by Lawrence v. Texas (2003).
No, it just means that the default position is that the last decision stands. The burden is on the side favoring change, but it can be done, and has been done, hundreds of times. Your "for eternity" is a silly bit of rhetoric -- we're not still living under Dred Scott or Plessy, to name the first two to spring to mind.
The alternative is chaos; if precedent is too easily overturned, then no one can know what the law is from day to day. If someone who tries to abide by the law cannot, there's something wrong not with him, but with the law. If I'm a hiring manager, am I required to consider race as a factor in hiring or prohibited from considering race as a factor in hiring? If I can't answer that, the only safe decision is not to even think about hiring anyone.
It's not an idle question. Absent a clear legal guideline, I'm guaranteed to be sued for my decision, no matter what it is. That uncertainty kills business, because the only safe decision is indecision.