i've seen one article that you posted discussing polygamy. even if gays are a small, vocal minority, there is no denying that gay marriage is very much in the national conscious as an issue. polygamy is not.
as for equal protection. here's how it works. equal protection means equal protection. however, if it was literally applied, then a substantial chunk of laws would go by the way-side as nearly every law discriminates against one group or another. the courts have attempted to strike a balance between permissible discrimination and impermissible. their analysis is as follows: they examine the purpose of the law and whether it is intended to discriminate against a particular group. they then decide whether such group is a "suspect class" entitled to a higher level of equal protection scrutiny. if the class is not suspect, they apply a "rational basis" test. this means, essentially, that so long as the gov't can come up with any old justification outside of pure discrimination, the law is ok. if the class is "suspect", different levels of scrutiny are applied. to date, only classifications based on gender and race have been labeled "suspect classes".
racial classifications are subject to "strict scrutiny". this means the state must have an overwhelming need for the discrimination, the discrimination is the only means of achieving this end, and the discrimination must be narrowly tailored to achieve only this end. it is a difficult standard to meet, to wit, no one has been able to satisfy its requirements.
gender classifications receive a middling level of scrutiny somewhere above rational basis but beneath strict scrutiny. for a law that differs between genders, the state needs a pretty compelling reason for the discrimination, the discrimination must be a means to achieve this end, but it doesn't have to be as narrowly tailored to achieve the end(i.e. it doesn't have to be the "least restrictive" means of achieving the end). this middle level of scrutiny makes gender discrimination based on something like intellect no good, while recognizing that there are still valid reasons for distinguishing between sexes.
now, with respect to gay marriage, the fight will be over what type of "class" gays are. my gut says it will get "suspect" status, and thus a higher level of scrutiny. as such, the state will need a pretty compelling justification to discriminate against gays. justifications based on morality and religion, which forms the basis for every justification i have seen against gay marriage, have not held up in court. if the court finds gays aren't a suspect class(which i think would be more likely if the courts decide being gay is simply a choice), then just about any old justification will do(i can't recall a situation where the court struck down a law based on a "pure" rational basis test.
the same analysis will apply to polygamy. if polygamists receive suspect class status, again, better justification is required. whether or not the court(or the court of general public--yeah, that's you vitus) will find this compelling, one CAN argue that there are secular, non-religious based justifications for precluding polygamy. for me, it's a much more open question of whether polygamists are a suspect class, and thus there is a likelihood that rational basis would apply. in which case, the rationale discussed previously would most definitely pass judicial muster.
that's how equal protection rights are determined and whether they are "baked" into the constitution.
f/k/a mclamb6