The smear campaigns are one of the surest signs that they have no data to back up their position. People with solid data generally welcome critics because it gives them one more opportunity to show how the data backs up their position, while people that don't have any such data feel threatened and have to resort to trying to shout down any and all questioners.

These people are NOT scientists and their tactics should be decried loudly by anyone that wants to consider themselves a real scientist.