OK let's see what ousting really is:
1a : to remove from or dispossess of property or position by legal action, by force, or by the compulsion of necessity
So I supposed there are three ways they can accomplish this: kill Ghadaffi, force him out of office and the country (either one of which would fit the term "oust") and lastly "convince" him that he should play nice and step down as the leader and let them all vote from now on. Of course this convincing is being handled through violence, and as we see from the definition above, this still fits the definition of "oust" (by legal action, by force, or by the compulsion of necessity).
I agree we are using force. however, we are not going "to remove from or dispossess of property or position". Obama has not called for us to oust Ghadaffi, and it is irresponsible to say he has.