Mike,I guess I am confused as to what you are trying to accomplish. First, you should not use the Message but rather the Text Value for a broken rule. The Message will always contain RTF as this is what it is designed to do. The Text Value is just a plain text message and does not support RTF. You can pull from either. The Message is designed to work in conjunction with our proprietary MessageForm which supports RTF messages. For a broken rule message, you should just use the Text Value and then you will not have any of the RTF tags when displayed.
Let me know if this is not what you were trying to accomplish.