Not sure that I understand (I'm not being insolent, I just haven't had my coffee this morning). Claiming that "humans are likely to over-estimate the chance of a hard-takeoff singularity in the next 50 years and should therefore discount inside view arguments on this topic" requires evidence, and I'm not convinced that the standard optimism bias literature applies here. In the absence of such evidence one should accept all arguments on their merits and just do Bayesian updating.