It could be one damage, I don't care - if you activate an energy field with something interrupting the beam, that "something" should get hurt somehow.
If this doesn't sound logical, then make a new line of shields with spikes that deal damage with a shield push.
Then add an achievement for killing an enemy with a shield push.
I'd rather see periodic push (e.g. one push every 5 seconds or so). For these times the place is so crowded the last pushback didn't work.