Rebels at the 3rd kinslaying

[Artanis]

The remnants of Fëanor's sons did not have full support from their own people during the attack on the Elven dwellings by Sirion:

For the sons of Fëanor that yet lived came down suddenly upon the exiles of Gondolin and the remnant of Doriath, and destroyed them. In that battle some of their people stood aside, and some few rebelled and were slain upon the other part aiding Elwing against their own lords (for such was the sorrow and confusion in the hearts of the Eldar in those days)...

So, they probably remembered Doriath too well and decided that enough was enough. But could their rebellion be morally justified? What about the loyalty that they owned their Lords? Was standing aside any better than joining the battle on the other side? What do you think?

Edit: I'll give you a proof of my poor English comprehension and ask a question ... does "slain upon the other part" mean that they were slain by the Fëanoreans or the people of Sirion ...

Edit2: And what do you make of "the sorrow and confusion in the hearts of the Eldar"?