Be really carefull what you wish for, because giving the seperatists weaponry to fight against Ukraine is one thing (and it's bad), but putting the blame only on Russia for a major fuck-up done by the seperatists (as already proven that they fucked up) is another.
If the seperatist pulled the trigger and they downed a civilian aircraft in place of a military one, then it's their fault and they should be punished to hell and beyond. Russia is (believed to be) responsible for shipping the weaponry, not shooting it. If they are proven to be more involved in it, then let them also take the blame.
EDIT: And before anyone says "giving them weapons is baaaaad!" - please recall the Cold War. Shipping weaponry to terrorists/seperatists/rebels was done by both parties as a way to fight wars by not involving in them directly.