Per The Last Best Hope, though, the Mars synths weren't sentient anyway, so the ban had nothing to do with that. Besides, we've seen in various series that holograms can become sentient considerably more easily and accidentally than androids can, given that nobody was ever able to replicate Soong's achievement (except Altan Soong).
Oh, absolutely, I'm not saying that kind of reasoning is rational at all.
Statistically, we have a lot more holograms go rogue than androids. But I think a lot more people will be worried about androids turning dangerous (which usually has something to do with becoming independent/sentient) than holograms.
The robots on Mars weren't sentient and any cyberneticist would have told you they were incapable of sentience, but I think in the wake of the catastrophe (and with the subtle pushes from Zhat Vash infiltrators) a lot of people will have become worried of a robot uprising. Hacking, too, yes. But also the synths actually "going rogue" on their own.
Meanwhile, holograms
have actually gone rogue in the past. Not usually without some kind of input (Moriarty and Fair Haven happened because people messed with the normal functioning), but you even find holograms that just... became sentient over time (think The Doctor). But apart from that last one, none of them have the same independence an android does. You can kill a computer's power source. It's much harder if the computer has arms and legs and many times your strength.
(Again, we've seen holograms take whole starships hostage, but if you weigh that against the millions of holograms interacting with people every day without issue, it must seem like almost a rumour or exaggaration.)
So on the one hand, you have holograms, who are being used all throughout the Federation as computer interfaces (like the Index) and recreation (holodecks) and occasionally as actual helpers (EHs). They are tied into computer systems (usually) and disappear if you tell them to deactivate (usually). And they can't follow you off the holodeck (usually).
On the other hand, you have physical beings, who you might maybe be able to turn off? But are they really turned off? And you can't do it by just saying a word. And they are much stronger and faster than you. And you haven't been trained from childhood to see them as easily controllable NPCs in your stories/computer games. And then they "go rogue" en masse.
I can see why people would decide to ban all research on synths but somewhat neglect the question of holograms. It's not at all rational. And I'm fairly sure there
are laws and systems in place that regulate holograms (there's mention of this in the books and I've seen other people do really interesting worldbuilding on that front, though we probably shouldn't discuss that here ). But as irrational as it might be, I understand why, in the wake of the Mars Attacks, the hammer might have come down on synths in a way that it didn't for holograms.
(i hope this isn't too incoherent, it's kinda late ;9 )
)
