There is no doubt that the Templars were different before Meredith, that doesn't mean the situation was better, just less tense. Given the amount of Blood mages in Kirkwall, a hardliner like Meredith is needed to keep the mages under control. Just like a hardliner like Orsino is needed to make sure the mages aren't trambled. As you may see, these two aren't compatible, certainly not when taken to extremes like Meredith and Orsino. Moderate Knight-Commanders and First Enchanters wouldn't cut it, becasue then the rank and file would get out of control faster.
Perhaps I should quote something in the game, at the beginning of Act 3.
Varic
The harder she squeezed, the more the mages resisted. The more they resisted, the harder she squeezed.
You can defend Meredith and the templars all you want because by the ancestors mages could never possibly be innocent of the supposed tension (sarcasm, by the way.) But Meredith was a hard liner who wouldn't compromise the least bit. In the beginning of Act 3, she wanted to make an example of Orsino, which probably meant kill or tranquilization, and the only reason she didn't give him a traitors death (and she was accusing him of treason) was because Elthina stopped her.
And Orsino wasn't preaching that mages were being treated unjustly. He wasn't saying templars are evil and need to leave. He was telling the crowd that Meredith had been acting Viscount for three years and not only is she not allowed to do that as a templar, but she was also not letting any noble in the city step forward to become the new viscount. She was abusing political power she should never of had to begin with.
I think it's important in the mage vs templar debates to keep in mind Meredith was in charge of more than just the templars at this point in the story. Heck, even when Hawke is getting off the boat into Kirkwall for the first time, we are told that Meredith is telling the city guards what to do and Dumar stayed out of her way.
And Aveline is pushing templars out her door constantly in Act 3 because the templars are trying to remove her from her position and take control of the guard directly.
Meredith was not just pressing down the mages, but the nobles and guards as well.