Two things would happen.
- They'd justify the ICE goon's behavior by claiming the embassy was enabling terrorism or drug trafficking.
- They would pitch a huge fit, take some sort of extreme action, and claim they're in the right because US diplomats are good guys.
They don't care about rules, ethics, or even having a consistent system of values. They only care about punishing people, power, and getting what they want when they want it. If they pull back at all, it's only because they fear their support (and with it their immunity from consequences) is slipping. They're just bullies and cowards.
Trump likes bribes. There's your answer.