Only in the very specific case of the post you are replying to. Elsewhere in this debate, plenty of arguments have been presented as to
why doing A might increase the risk of Z. Some (knowledgable) groups are claiming that this scanning would be illegal in the EU, others that it might be unconstitutional in the US, and/or that the clauses in the T&Cs whereby users agree to this are unconscionable - if Apple wins a court ruling on that subject, it could set/break a legal precedent which would make future expansion easier. Then there's the self-evident fact that by
possessing the facility, Apple could be legally forced to (ab)use it - true, they could also be legally forced to create such a facility from scratch, but already having the infrastructure makes it
easier.
Also, if you follow these threads you'll see some people defending Apple by saying something like "your photos are only checked if you choose to uploaded them to iCloud"... When did it get to be OK that your photos can be scanned on iCloud? Did people dismiss any fears about that as "slippery slope fallacies?"
Anyway, these "logical fallacies" sites themselves tend to play to the fallacy that every debate is over a "falsifiable" fact that can be proven true or false. They mix up genuine logical fallacies of the "Dogs have 4 legs, Felix has 4 legs, therefore Felix is a dog" variety with common argument tropes that are often used as weak or fallacious arguments. Or to put it another way "Bob used 'slippery slope' in a fallacious argument, therefore all 'slippery slope' arguments are fallacies." - To be fair, most of them cover themselves once you read past the first sentence.
Still, from that site, "Want to share this fallacy on Facebook? Here's a button for you:" is the funniest line I've read all week.