It's not "illogical" to say that a culture which executes homosexuals is inferior (in that aspect) to ones that don't. You can argue about the standard, but it's straightforward and logical.
For instance from my perspective a culture that doesn't allow gay marriage is clearly inferior, which is straight forward and logical.
But the coastal culture I live in now and am originally from doesn't view it that way. I get a lot of these culture-clashes daily and it's a really hard thing to figure out. Mainly because life is truly how you view things, and your worldview builds your reality — but how can one say one worldview is better than another, objectively? Because the observers worldview makes them biased, it's really hard to say.
So, yes, every time you see a statement along the lines of "society X is better than Y", it comes with an implied "Based on my values, ...". But precisely because it is always there, there's no point spelling it out every time.
The problem is: it isn't always there, even when it should be. Some people actually mean "Society X is better than Y in an absolute, not relative, sense."
But even then, "Based on my values ..." is implied. It just comes with an assertion that those values are universal (which, if you're a cultural relativist, you'll treat the same as well, recursively).
A particularly annoying one is when people lie about their values or worse claim that their argument doesn’t stem from their values (are they embarrassed?), it’s purely “rational” and anyone who doesn’t agree is pc virtue-signalling cuck who is blind to reality.
Most political debates here for instance would be a lot shorter if people stated their cultural values upfront, rather than concealing them and arguing about something tangential.