Does digestion require hydrochloric acid?
Parietal cells use ion pumps to expel protons and chlorine ions into the lumen, which create the necessary acidic environment to denature pepsinogen into pepsin.

It is the low pH environment that reconfigures or denatures pepsinogen into pepsin. The acid used does not matter. For example, one experiment in classifying properties of pepsinogen used a 3.5 pH solution of 0.5 N sulfuric acid to activate pepsin.

We evolved stomachs with parietal cells that use an energetically expensive process to maintain the acidic gradient necessary for digestion and protection from pathogens. 

It may be that biochemical pathways to generate other acids did not evolve, because it is either energetically cheaper for these cells to make HCl, compared with other pathways that would generate other acids of sufficient strength; or the relevant chemical components involved are more abundant than others in what we eat and drink, and thus easier to make in quantities needed for digestion and defense. Chloride ions also serve a role in maintaining intra- and extracellular fluid pressure and thus play a larger part as electrolytes in the normal function of the body — they are available and cells use them.

But to answer your main question, an acidic environment activates pepsin, and it is not chemically necessary for this to be created by hydrochloric acid.