I believe that the statement, "A person commits a federal felony when he ... knowingly assists illegal aliens due to personal convictions," is overly broad and severe, and unsubstantiated by the citations listed.
In the article's footnotes:
"It is unlawful to hire an alien, to recruit an alien, or to refer an alien for a fee, knowing the alien is unauthorized to work in the United States ... It is unlawful to hire an individual for employment in the United States without complying with employment eligibility verification requirements." The bar is set pretty low. A social security card and driver's license are sufficient proof of eligibility to work.
"Employment includes any service or labor performed for any type of remuneration within the United States, with the exception of sporadic domestic service by an individual in a private home." The footnote cited only deals with employment on a fishing vessel.
"Harboring or aiding illegal aliens is not protected by the First Amendment." After looking at the case cited, it seems to me (I am not a lawyer) that the case decision refers to conduct that is specifically and knowingly intended to circumvent immigration law. I do not believe that feeding someone who is hungry or housing someone, without specific knowledge of their illegal status, would be covered.
"It is a violation of law for any person to conceal, harbor, or shield from detection in any place, including any building or means of transportation, any alien who is in the United States in violation of law. Harboring means any conduct that tends to substantially facilitate an alien to remain in the U.S. illegally." The article leaves out the critically important word knowingly from both sentences, and there does not appear to be any law requiring a person to know, except checking eligibility to work.
"A person or entity having knowledge of a violation or potential violation of employer sanctions provisions may submit a signed written complaint..." It says may, not must.
"The 1996 immigration control legislation passed by Congress was intended to encourage states and local agencies to participate in the process of enforcing federal immigration laws." Again, it does not appear that local agencies are required to do so.