Were there really issues with wildlife being affected by white light, say form MV lamps, before the days of HPS? Other than sea turtles I was never aware of any major wildlife issues caused by white light at night. And who cares about astronomers. 
Never understood the whole big deal about space exploration personally. We need to sort out our own issues here on earth before we start causing issues on other planets... 
The thing is, with the coming high efficacy light sources there became way more and way stronger light sources installed everywhere.
It goes so far, although the efficacy of the light sources is now 10x than it was 100 years ago, the total power consumption used for lighting becomes 10x higher as well. That means today we emit 100x more light than we used to. And that is the main problem for the light pollution in general.
The thing is, the lower cost of the artificial lighting promoted its way wider use, include the "architectural lighting" (illuminating everything, mainly with light sources shining upwards) madness.
And regarding the LPS (as a monochromatic light source) sometimes presented as a solution to the light pollution:
Although the astronomy is very important, the light pollution impact on other life, humans as well as wildlife is important much more.
So although LPS may solve the light pollution problem for astronomers, for the rest even the monochromatic light is still the same light pollution. And because the LPS is way harder to control (the beam pattern) than the real HID or LEDs, it becomes way more potent source of the light pollution than most other light sources (maybe except fluorescents, but these are not that wide spread for the outdoor street light duty).
So the LPS solution may make sense really in the close vicinity of the observatories, as general lighting they makes the light pollution only worse.
The only working solution to the light pollution is to really generally reduce the use of artificial illumination mainly outdoors. Illuminate only what needs to be illuminated and with only just enough intensity, not more.
I think it is generally happening, at least partly: Because the LED system prices generally scale with power rating, there is a strong incentive for the utilities to really specify the minimum power needed for the lighting. With HID this was not the case: Very frequently the lower power system cost the same, sometimes even way more than its higher power brother, which led utilities to keep using the same power (e.g. 250W HPS or MH in place of older 250W MV) even when the new source had way higher system efficacy (very often a modern 70W HPS or MH with good beam control was able to perform the job of an original old 250W MV system).
By the way the LEDs should be able to lessen the problem really generally, if properly used and designed (include color quality - without aiming to too high CRI). They are small and compact, so rather easy to control their beam to illuminate what is needed without any significant light spill, with most energy in one blue line, so similar as LPS easy for astronomers to filter out the residual glow from that most energetic component). Of course, for e.g. observatory parking lot and such close proximity that may not be sufficient, but those could well be lit by e.g. narrow band green-blue LED types (they are way less efficient, but still offering good optical control and monochromatic output; we are talking about special use where the efficacy does not have to be of the top priority).
