Indeed they cannot merely say "because I said so"; they rather need to churn out some written sophistry to justify the decision they would personally like to make anyway.
That's just legal realism. The problem comes not with an
individual case's disposition, but what that disposition might be used for later as precedent. I'm going to give you an example using a presumptive challenge to
Obergefell.
A conservative scrotus supermajority, as I described earlier, can't attack
Obergefell without basically invalidating
Carolene Products footnote four and throwing strict scrutiny out the window. Footnote four is such an overwhelmingly strong precedent at this point, regardless of individual justices' ideology, that it has completely overshadowed the case upon which it is based (a straightforward
Commerce Clause question, this will come up later) and at this point carries the judicial might of a full-on Constitutional amendment. It's nearly as important to 20th and 21st Century jurisprudence, as
Marbury v. Madison which is the case establishing judicial review in the first place.
Footnote four is at the heart of
every single civil rights and liberties case that has been put before the Court since its authorship, as it is the basis for which standard of review applies. That includes the Second Amendment.
Conservative court throws footnote four out the window today in
Homophobic Peckerwood v. GLAAD, liberal court cites
Peckerwood to apply rational basis to
Yeehaw Rednecks United v. Gun-Shy Liberal Fop tomorrow.
Now, remember my earlier allusion to the Commerce Clause?
Such is not a great barrier, and has been done countless times to overturn laws that were perfectly legally sound, but which the justices did not like.
So in
Heart of Atlanta Motel, the Court's only legal basis for upholding Title II of the 1964 Civil Rights Act was...the motel was near an interstate. Literally, that's it. The Court had to rely on one of the most laughably overbroad interpretations of the Commerce Clause in US history, and a fucking map, to uphold the
1964 Civil Rights Act.
Likewise,
Griswold saw the codification of William O. Douglas' famous "penumbras" argument to establish Constitutional basis and protection for unenumerated rights (in this case, privacy), in the face of the then-prevailing legal maxim
expressio unius est exclusio alterius, under which there is
no fundamental right to privacy. In other words, Douglas cut an entirely new legal principle out of whole cloth, hoping it would stick and that later Courts would not be so foolish as to challenge it. Privacy isn't an "emanation" of the First, Third, Fourth, Fifth, and Ninth Amendments; it's the
foundation for the First, Third, Fourth, and Fifth Amendments.
And to be quite honest,
Roe was one of the
weakest precedents in the Court's history. Norma McCorvey had already given birth by the time the case was granted cert; it was therefore moot, and the Court had to fabricate basis for itself to hear the case. Which was the Court's very intent -- it wanted to create basis for jurisdiction in controversies that would never see cases make their way to it
before they became moot. And last but not least, McCorvey's standing was questionable (to say the least) as she'd perjured herself in her attempt to secure a legal abortion in the first place, having falsely claimed she'd been gang raped by black men.
Which is why the pressure was on Congress to codify
Roe in federal statute, in the first place. Now it's "merely" going to take a Constitutional amendment, and good luck with that.
So...what you're saying? That's a two-way door. Be careful --
very careful -- what you wish for.