That would be a different argument and case. If Congress were to pass a law providing blanket immunity of federal employees, expect it to be challenged on cons

That would be a different argument and case. If Congress were to pass a law providing blanket immunity of federal employees, expect it to be challenged on constitutional grounds especially in a case where the damages were the result of misconduct. All the SCOTUS seems to be saying here (my interpretation) is that if the desire is to provide any level of immunity for government employees, there needs to be a law passed explicitly saying that. Whether or not the law passes constitutional muster is an argument for another day. This is definitely a slippery slope situation.