What I think is going on is not that people like what Spartans actually did, people are simply enamoured by their honourable and majestic portrayal in popular culture. What youngster does not fantasise of being that small and determined band of soldiers that holds off the hordes of brutal barbarians, only with their shields, spears, courage and martial prowess? Who doesn't want to be part of that 250 men that defy a whole empire, _and succeed_, immortalised in songs and poems? (I mean they all die by the end, but they do kinda succeed in their mission).
The way I think about it is that for me there are two (or more even) Spartas. The historical "Sparta" that were brutal oppressors, like a case study how _not_ to structure a society, lots of lessons to learn from it. And the mythical "SPARTA!" one, full of honourable dudes and courageous women, that we can aspire to be, even if they were not real. No reason why they can't coexist in our minds, we just need to be careful which one we talk about.
When people say they "like Sparta" I don't immediately feel that they are silently singling that they will be ok with slavery and secret police, I think they want to be strong people fighting to protect their brethren, and that's generally OK with me.