Errors in English in Quotes

Many quotes from different sources involve translation from another language. I noticed a statement from a Taliban spokesperson today that has a grammatical error in English. The error is not that serious, "endorses" should be "endorse" to agree with "we". I think perhaps one should put "sic" in parentheses next to the error. However in another post I noticed a translation from a Golden Dawn statement in Greek had several more serious grammatical errors. What should one do? It seems improper to edit a quote but some of these automatic translation aps often come up with mangled English.