Regarding your first example about health insurance, that's an issue which would be more productively dealt with by advocating for socialized medicine - a complete nationalization of all healthcare industries.
I'm taking as given how things are. You're talking about a separate issue.
If your complaint is about policies that cost lives, then this could be just as easily laid at the feet of anyone and everyone who refuses to support socialized medicine - and that includes the myriad of Democrats who gushed over Obamacare and thought it was such a great thing.
That's right.
As for your second example regarding the hypothetical kidnapping of a same sex couple's child, that would still be kidnapping, and it could just as easily happen to a couple which is legally married. Those who oppose gay marriage are not advocating kidnapping anyone, so I don't see how you can charge them with that.
The rights of marriage include protections for spouses who aren't blood relations of their kids (e.g. where one parent in a same-sex couple is the biological parent of a child who they raise as a couple). If the biological parent dies, custody generally goes to the spouse.
However, if the marriage isn't recognized by the state, then custody generally goes to a close blood relative.
In many cases, this has resulted in the child of a same-sex couple going to an anti-gay relative who denies the surviving parent access to the child they raised.
A lot of the main arguments would have also been dealt with by allowing civil unions, which is something that conservatives were willing to support. It would have entailed all the legal benefits of marriage without actually calling it a "marriage," which was the main thing that bothered the conservatives.
Enough conservatives disagreed with this approach that prohibitions on giving "the benefits of marriage" to unmarried couples. In the case of Ohio (I think it was Ohio), the crime of spousal abuse was deemed to be a "benefit of marriage", resulting in hundreds of spousal abuse charges against people in common-law relationships being dismissed. Apparently, civil unions were so odious to some conservatives that letting a bunch of wife-beaters off scot free was considered the better option.
And in any case, there is no civil union arrangement that gives all the rights and benefits of marriage.
That seemed a reasonable compromise, but even that was not enough.
"Separate but equal" is never a reasonable compromise (or actually equal).
As far as thinking deeply enough about the issue, it depends on how "deep" down the slippery slope you want to get.
There's no slippery slope. Just think about what the rights of marriage are and how they're used. Saying that you want to ban same-sex marriage is effectively saying
"in the circumstances where those rights will matter to you, I want to make sure you don't have them." Understand what rights you're trying to ban and what the impactsof your actions will be on real people and real families.