Regarding the URSS, of course persecuting and banning religion is not the way to go, I'm not biased to say religion is the only cause of harm in the world or that it has only negative effects, it certainly has positive benefits, they are just far surpassed by the cons.
Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you