You know Anon, I don't think it's really a "letter of the law" thing.  I think that they are simply anti-immigrant.  They wrap themselves in the righteous cloak of the enforcement of our laws, but I think it's all just a cover.
Normally, when we have laws that don't work, we change them.  But too many don't want rational immigration law.  They want it to be harsh and punitive, so that they have an excuse to keep attacking immigrants.