I'm glad you brought this up. Terri herself is driving this narrative. The evidence that people are discussing here is based on Terri, her movements and her own words.
The smearing of her reputation has come from Terri. The lies she told - recorded in her own words, in her own email and text messages that are publicly available for all to read. This isn't innuendo. This is Terri getting revealed to have used her own baby as a lie-shield to go try to have sex with a man while searchers were out in the woods looking for her stepson. This is Terri giving up her baby, so she wouldn't have to contribute to the investigation. This is Terri buying secret phones and throwing them out during a kidnap investigation.
So yeah - it's a smear campaign, but it's Terri herself who smeared her own reputation with her lies and complete lack of concern for her missing stepson, followed by her complete lack of concern for her baby. Public sentiment was shaped by her own words and actions. People do tend to be rather unforgiving of people who show themselves to be of that character.