It's not up to you to decide whether or not you should witness to the church, it's up to the Pastor. If you feel you have a message from the Lord for the church then go to the Pastor and present it to him and ask him to let you present it to the church. If he refuses then try another church/Pastor.
Be aware, though, that God could be working in these churches and Himself causing turmoil. Pray about it before you act.
Blessings,
Alan