I would like to suggest that sidepath is to surface street as surface street is to freeway is not quite an accurate comparison.

I can ride just as fast on a sidepath as on a surface street. That you cannot means only that you are capable of faster cycling than me, not that the sidepath is has an intrinsic prohibition to allowing cyclists to go as fast as they want.

I find that the main consideration with sidepaths is learning to negotiate the relative dangers. They are different and require different tactics. Just like there are different dangers and tactics on the freeway or on surface streets, or different dangers and tacicts for when you drive a truck or a motorcycle.

JF's failure was that he didn't adjust his riding style to suit the environment. This is exactly his complaint about most cyclists on the roadways. That they don't adapt. Had he adapted to the conditions he might have found them to be just as safe as what he's used to.