I never disagreed with the scriptures!!! - but my point is, before you rebuke or warn people of another ministry or person's sin, I think it is best if there is time spent in prayer and you have peace in your heart from God about rebuking that person or ministry.
You shouldn't just rebuke or warn because their actions make you feel uncomfortable to you. And you shouldn't rebuke or warn if you have never experienced the ministry. You should also never rebuke or warn if you are solely relying on someone else word, as that is hearsay/rumour which in turn would be considered gossip.