Why is it that so many anti immigrants don't care about punishing those who employ or house illegal immigrants?

technically if someone against undocumented immigrants being in the US then that person should be against any business that hires undocumented immigrant weather it be a warehouse, fast food place or a private construction company. If anti immigrants want undocumented immigrants to leave the US then why not boycott and picket the companies they know hire undocumented immigrants. Honestly speaking how many undocumented immigrants are hired or serve an anti immigrants