You point is true for all organisations that cover many issues, and do not concentrate on one single small issue. You end up not donating to anything, even if your donation would have a large net positive.
Tagging money for specific issues is problematic because the organisation doesn’t change its budget percentages for small donations (money is fungible), and organisations find tagging difficult to manage [TODO insert article link here].
I've been in organizations that allowed earmarked donations for certain funds / projects. The ACLU can totally allow earmarked donations for projects they are undergoing.
Ex: A policy of %80 towards earmarking & %20 towards the general fund to help boot up new projects / general admin would be totally fine with many donators.
Organizations that say that they let you donate to fund specific issues are fooling you, unless the amount you plan to donate is huge. The reason is that money is fungible. Let's say I need $200k to fund issue A, and $200k to fund issue B. You say that you want to support only issue B. Fine, I just put your money in the issue B bucket and move a corresponding amount of unrestricted funds into the issue A bucket. Unless almost everyone restricts their donations they can always do that. They can backfill any unrestricted money to fund any of their priorities that are, for some reason, less popular with donors.
That only works if earmarking for issue B is not common, but if some media story suddenly made earmarking for issue B 50x the general fund / issue A, by people in aggregate, your not going to be able to do that well.
What you talk about is much like the arguments against voting, while such logic makes society lose it's prisoner's dilemma for change.
Call them and ask. There is usually a fund manager who can direct the money into different causes at the benefactors wishes. Now, if you only donate a minimal amount that will go in to the general fund. They wouldn't expend the same energy for a $35 donation that they would for a $3500 donation.
If it's a civil rights case and there's merit to your claims, you might be able to find public interest lawyers to help out for much less than that. Call around, there are firms in most large cities.
I've contacted one. They said we have a case, but that the federal courts don't really care about rights violations unless there were substantial financial impact. In theory, the DOJ is supposed to investigate our complaint and take injunctive action to correct any agency policy, practice, or pattern that violates the rights of defendants/people. We'll see how that actually works, but I won't hold my breath.