Even if you don’t answer their arguments, it wouldn’t hurt to research the pro-life objections to counter their points in the future (whether it’s with them or whoever else God sets in your path down the line) There are numerous books and material available. Sometimes timidity is the result of not having enough confidence in the matter being discussed. I was that way years ago when someone would attack the Catholic Church. Since I didn’t know too much about my faith, I remained silent. After one particular nasty attack, it finally lit a fire within me to defend what I knew in my heart, I loved. I researched and found answers to their arguments, and I was able to hold my own pretty well.
However, I understand what it feels like to be overwhelmed by the sheer amount of viterol that can be lobbied by those who are quite passionate in their pro-choice views. It may not be wise to respond at that moment in time. The best response is prayer because as St. Paul says, in the end, we don’t wrestle against flesh and blood, but against the principalities of darkness. I think if we could clearly see the power that happens behind the scenes when we pray, that would more often be our FIRST recourse instead of our last. Other times, it would suffice to simply say, “I disagree.” However, if you feel like the Holy Spirit is calling on you to speak up, then you should do so.
Either way, whether you choose to speak up or not, at the very least pick up some materials that counter their arguments. That way you are equipped to speak for those who have no voice when the occasion arises.