On the face of it, that isn't a plausable premise. If it were, then kettle souring and wine fermentation wouldn't be possible.
Yeast want a pH of 4.2 to 5.8 for optimal conditions, but can reproduce, ferment and survive conditions as low as 2.5 pH. Though, being outside of the optimal range is going to come at the expense of "clean" flavor. Yeast isn't concerned about how the beer tastes, only in consuming sugar.
Yeast tend to lower the pH of wort during the lag phase, but very low pH can extend the lag phase as the yeast have a harder time converting wort proteins to metabolic uses for budding. Fermentation still happens, though. The pH for a fermenting beer is 4.4 to 4.6. Yeast tend to clump together and flocculate when the pH rises at the end of fermentation by 0.2 pH.
Proper (and commonly known) brewing practices yield good beer.