Originally Posted by Mr-No

Well, depends...
If that happened in your house, or house of some of your friends, then, yes.
Otherwise, if Canadian laws are at least a little similar to continental EU laws, then it isn't so easy to give answer.
Did you verbally provoke attack or not that doesn't matter at all, because if you verbally provoke somebody he can simply go away... There is no self defense in case of verbal attack (maybe some other things as "affect").
If you attacked first, then everything about self defense can be used on your opponent.
In accident which you describe, your opponents don't have self defense case, because they already had possibility to evade (I mean after first fight they get away form that house, maybe affect). When they return to the house with bats they are becoming attackers. So:
First, did you have possibility to run? I mean, you were been in corner with no way to escape? Threat was been so serious that you was been afraid for your life (e.g. 5 years old kid with bat isn't serious threat to adult), or life your close relatives?