When has the argument "We will probably loose, so why even try" ever justified not fighting?

You are right: getting Roe overturned is an extreme uphill battle.  Eradicating abortion from this country is, right now, a dream that will be extremely difficult, if not impossible to achieve.

First: so what?  Sometimes the end result does not matter. What matters is the choice to go down swinging.  We pro-lifers will keep fighting.  Second, and more importantly: with God all things are possible.  When God is for us, who can be against us?  We have God on our side.