I have yet to see any ASAT tech, from any country, that isn't mutually destructive.

Kinetic ASAT weapons create debris that affects everyone in space.

EMP ASAT weapons would also affect nearby satellites. For example, if they wipe out their own Glonass satellites, their own weapons systems (which are dependent on Glonass) would suffer - and their ground-based systems (Loran) has limited cover and accuracy. Goodbye to weapons that need accurate navigation/guidance.

It is mentioned that these would be some absolute last ditch measures...so do keep that in mind. About as last ditch as conventional use of nuclear weapons. If that time comes around, we're all going to be pretty screwed either way.