:::::The quotation you have given doesn't say Bismarck feared the popes "would use the infallibility dogma as a political weapon for manipulating Catholic voters": it speaks instead of relations between the popes and governments.  I think you should rephrase your statement to correspond to what your source says. 
 :::::You have made no attempt to deal with what I called the more important question: On what grounds do you say that the fear that you attribute to Bismarck was well founded?  That statement seems to be just an expression of your own personal judgement alone.  That's what is most crying out for sourcing, and it would be doing so even if you found a reliable source for your statement about what it was that Bismarck feared.  You shouldn't have removed the "dubious" tag without, as requested, discussing the question.  Will you respond now?