I am not saying that it should be scary to fight the government.
Here is what I think (obviously not the trial judge would think so don't hold me responsible if I am wrong):
First, some jursidction porblems. A state court would not hear such case due to inter-government immunity and a state court can not regulate the federal government. Vice versa. This is a separation of power issue so that any judge would know.
The following will be based on a suit in a federal district court":
I tend to think all the immigration laws, statutes, and such were based on 8 USC 1101, amended in 1993 by the Congress (I believe). In that law, Congress gave pretty much a plenary discretion to the attorney general and the secretary of homeland security. When I read that code, I felt like basically the FBI and USCIS can do anything they want, as long as what they do is reasonable. In immigrataion, Congress has the absolute power to regulate so that as long as anything USCIS/FBI would do does not fall in some kind of constitutional guarantee, such as race, alienage, or ethnics, a court will defer to Congress and the executive branch. This, obviously, should be the basis to challenge FBI/USCIS if there is a chance.
Even if FBI/USCIS did discriminate upon race or alienage, it does not guarantee the government will lose. The court will use strict scrutiny review to require the government show that the law is narrowly drawn to further a compelling state interest. I don't have to tell you that anti-terrorism is the top priority in this country and it is easy to show a compelling state interest by the government. If the law is overbroad, such as "anyone from Asia must be screened for three years", it will be struck down. However, this is regarding the conduct of FBI/USCIS so that I doubt they would have a policy like this.
Some years ago I saw a TV ad. A local lawyer said if you waited too long you should challenge based on some kind of statute. I immediately contacted the congressman in our district and what he said is basically like this. Anti-terrorism is the top priority and if FBI needs to do name check for 30 years you must wait. He did mention something about separation of powers but I think those were less important. The bottom line is, it is extremely heard to find the government is doing something wrong. The court abhors somebody challenges what is supposed to be a political question that it must defer to the other two branches.
That is why I think most advises from this forum to encourage you to get a lawyer are well on the point. To me, an immigration lawyer is not the one you are looking for. You need somebody such as the ACLU. I understand ACLU handled a lot of immigration cases.
Good luck on your hearing.