If every paper company got together and denied service to ICE, then ICE would be forced to limp along without paper. They wouldn't cease to operate - even if they wanted to, they couldn't; that's not up to them. They would just operate inefficiently. It would be frustrating to the DHS officers, but actively detrimental to the immigrants in their custody, slowing things down even more. Unless you actually believe that immigration law shouldn't exist or be enforced, you should be happy to work with ICE to help them process detainees as quickly and efficiently as possible.
"If we don't sell to XYZ someone else will" is not an argument to keep selling to XYZ, unless you already agree with (or are indifferent to) XYZ and their activities.
"XYZ is doing bad things but it'd be even worse if they did bad things less efficiently" is not an argument to keep selling to XYZ, unless you already agree with (or are indifferent to) XYZ and their activities.
Making an organization less efficient, or otherwise slowing an organization down, is not going to single-handedly stop it, but that doesn't make it pointless or counterproductive.
For the concrete example here, you haven't provided evidence that "less efficient" or "slower" applies only (or disproportionately) to activities that stop hurting people rather than activities that hurt people.
Also, you've created a false dichotomy, dismissing the existence of people who agree with portions of a branch of law but disagree with how that law is enforced.
I agree, I think its not an apples-to-apples comparison, and that is slightly intentional. I want to highlight the same decision to be made under a less frictional commodity to ask the question: where does one draw the line on what they supply? There are some obvious lines probably. You would not want to be a gun manufacturer that sold guns directly to drug cartels, for example.
I think it's reasonable to say "this software is open and anyone can use it, and we don't control who downloads and runs it themselves".
I also think it's reasonable, given an entity you don't want to do business with, to say "we don't enter into contracts (even our standard contracts) with these entities, and we don't provide any kind of support to these entities".
Furthermore, there's a difference between "someone bought this commodity from a distributor" and "we have a contract specifically with this entity".