Why is PerfectForwardSecrecy considered OK, when it has same defects as salt-less password hashing? PFS suites suffer from the same defects as any other salt-less password hashing scheme.
Why is everyone promoting Perfect Forward Secrecy (PFS) ciphersuites so fiercely?

Namely, when the group/hash weakens, then the attacker can invests into a massive pre-computation, after which individual connections/hashes can be broken with minimal additional cost. This property allows the big players to amortize the cost of the massive pre-computation over the massive ammount of cracked connections. Consequentially, it promotes mass snooping over targetted attacks.

This question is motivated by the WeakDH/LogJam paper.

EDIT, thanks @steffen-ullrich, It does not make sense to include the salt in "the secret", so the DHE equivalent of salt-less is "everyone uses the (few) same groups".
Salt-less password hashing is only a problem since the amount of passwords actually used in practice is comparably small and also not evenly distributed. Thus it is both in terms of time and memory possible to generate a table with pre-computed hashes and then check the salt-less hashes against this table to reverse the hash. The protection against this are thus salts (increase of time and memory needed for pre-computation) and slow hashes (increase of time).

But, this pre-computing will no longer be feasible if the choice of passwords is not biased against "few" often chosen passwords but if instead there would be a huge amount of possible passwords and none of these would be more likely than the other. It would simply not be practically possible in terms of time and memory to pre-compute and store the hash for all possible passwords. And that's exact the case you have with PFS - it is simply impossible to pre-compute even a relevant small part of all the possible values.