In reality Itachi had no choice at all,it was either kill his own clan or be killed alongside them.Danzo did use emotional blackmail to get Itachi to do it though.
I agree with that. But imo, the form of blackmail (it is definitely blackmail) used here doesn't quite correlate to the manipulation that happened to the other Uchiha. Mainly because, Itachi couldn't really do anything here. I don't think it's right to classify this situation with the other Uchihas, mainly because with the others they believed whole-heartedly in something that was a lie and had a choice on whether to follow up on those beliefs or not, only to find out that it was worth nothing in the end and that they were trolled hard. At the end, the Uchiha bar Kagami, Shisui, and Itachi didn't know what they were really being set up for.