Politicians are terrified of the protests, but they are even more terrified by the prospect that the protests could continue past the end of the school year, spilling over the bounds of the campus and into a long, hot, summer. It is the responsibility of anyone trying to stop this genocide to ensure that their nightmare becomes a reality.
That level of conscription would be far too destabilizing in the imperial core. I think that they have been successfully psyopped to be a garrison in a way that a multiethnic society without the same conditions or history would struggle with. Perhaps the most successful radicalization project the west has ever undertaken. As the ROI starts to drop you can probably keep enough people there to bleed Iran in one last crap shoot. The ones from North Africa and West Asia would probably have a harder time fleeing than Ukranians at this point.