First let me say that I admire your courage in the face of such close (and strident) opposition. I have known many in the RCIA process who faced similar challenges, and it’s not easy. I will pray for you.
Now:
Since your daughter in only 15 months old, these nasty comments are really directed at you. I disagree with people who advise you to “sing-song” some retort to your daughter, as that would be the same kind of sick triangulation they are using, and uses your daughter poorly.
So I suggest you communicate something along the following lines to your folks:
*Mom and Dad:
We are aware of your opposition to our family decision to enter the Catholic Church.
We don’t want that to turn into a hurtful situation for anyone.
Please know that we will never teach our daughter that your religious beliefs are wrong or bad, and we hope you will not try to teach her that ours are. We will teach her to love and respect you, and hope you will always communicate the same to her about us.
As for religion, let us focus on what binds us together in that regard…which is the teachings of Jesus. Therefore let us show to her a loving, caring family.
Our greatest hope is for her to grow up in a family-centered environment, and to experience the wonderful gifts of loving grandparents in her life.
To that end, we think it might be best if we all refrain from religious discussion that focuses on difference among churches, and rather focuses on what binds all Christians together. Can we perhaps come together and decide how best to proceed?
We love you,
Fred and Ethel*