Yes they did say, and said explicitly, it does not create that sort of slippery slope but the reasoning, those firm principles upon which it rests are not terribly firm. Ultimitately it creates a constitution that says whatever the judge says that it says.
Heck you probably could have overturned the Texas law based on 14th Ammendment but they over reached and that will come back to bite us.
You may not like the reasoning, but the reasoning was firm.
There was obviously no compelling State interest in keeping sodomy illegal for a small minority of the population, and legal for the vast majority.
The State on one hand, recognized the right of some citizens to engage into what Texas defines as "deviant sexual intercourse", but not others.