This is not the first time an airline rebrands an airplane due fearmongering after an accident. The Fokker-100 was rebranded as MK-28 in Brazil after an accident (trust reverse deployed after take-off). The news reported every incident with the plane afterward. I remember my parents avoiding flights with Fokker-100. The MK-28, on the other hand, had a very good safety record.
Is it appropriate to call this fearmongering when the issues are real (for the 737)?
The planes with the faulty software are grounded and won't be flying until they new software is proven to be safe. The re-certification process will likely be stricter than usually is. Thus, any fear about flying in those planes are unjustified.