For the longest time, I was indifferent towards the naysayers, but now I know they were right all along.
For the longest time, I was indifferent against the naysayers, but now I know they were right all along.
For the longest time, I was indifferent towards the naysayers, but now I know they were right all along.
For the longest time, I was indifferent against the naysayers, but now I know they were right all along.
The adjective "indifferent" always idiomatically takes the preposition "towards."