I wouldn't call it seditious.
It's actually exploitative, on both ends but one worse than the other.
H1Bs wind up feeling forced to work far more hours than they should, but then it adds pressure to any in-house employees to work more than they should too.
It's extra evident in the people that go from H1B to full citizenship, they often never learn to just take a break, sometimes to their own detriment.
Overworking H1Bs isn't what people are concerned about (yes it's an issue and part of the problem because it's an extra incentive). Importing people to supplant the local talent who are more than capable of doing the work, widening the labor pool to weaken labor's power, claiming it's "meritocracy" and that everyone who doesn't agree is somehow racist or "illiberal" are the core issues.