This is not "slippery sloping". This is analyzing what the proponents of said policies want to achieve, and have achieved in the past. Maybe it's not a conscious decision, but many of these proposed voting laws, or ones that are implemented seemingly effect specific demographics.
Factually and statically, these demographics don't vote in favor of the ones proposing these policies. Said demographics are often of lower income, working longer hours in physical labor jobs.
> ... nobody has suggested discriminating based on which IDs.
From this link https://www.nbcnews.com/politics/2024-election/voter-identif...
"Missouri state Rep. John Simmons, a Republican who sponsored legislation requiring a state-issued photo ID, said that election fraud cases are low priority for prosecutors and that requirement is a “commonsense” way to prevent such cases."
I understand your wording wasn't precise, but requiring a photo ID is specifying "which" type of ID is required. Yes, it is still a vague category but it is narrowing what type is acceptable.
To tie it back to the demographic I mentioned, it may pose a more difficult challenge to acquire a photo id than one would imagine; from my understanding these photos must be taken at an approved institution like the post office. In many of these low income communities, a post office will not be nearby, and due to a lack of transportation it may be quite difficult to get to the place to take the photo.
Ontop of this, the jobs these people are working are far less forgiving with freetime, or taking breaks to do anything not work related when compared to a "cushy" engineering job; for these people, getting time off may be difficult (though I was under the impression that's illegal in many states, I thought an employer is required to), and the money they lose out on could mean not being to afford an important commodity/bill.