They suck. You don't. Who are they to judge how you parent your kid? You know your kid, your family, your situation best.
I too have a teen that needs to be pushed. She likes certain sports/activities but isn't naturally inclined to seek out opportunities to improve at those things in order to continue to qualify and make teams down the road. So her dad and I push her because we know better than her 14yr old self, what she needs to do to stick with it (which she tells us she wants to do). My other DD is the exact opposite. She'll work and work and work tirelessly at the thing she wants and be firm in telling is what she doesn't want. We know if she's no longer interested in something she truly means it and we don't push.
So, easier said than done, but I'd try to let their hurtful words go.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.