Draft notice (feel free to make any tweaks to this notice but do not vandalize or make unconstructive edits):
If you want to downgrade a source that was previously established as generally reliable, you must provide substantial evidence the source's factual accuracy is compromised and thus the source's should be considered unclear, borderline or questionable. Remember, perceived bias does not equal unreliability. Publishing a few articles you don't like is not a reason to immediately open a discussion to request a downgrade.