If you mean that it's the pegs that are breaking off, and the fitting that they are part of is glued to the drain line here is how to remove it at the glue joint.
With a hack saw cut it off at the glue joint.
Then with a hack saw blade cut 2 slots, about 3/4in. apart, in the part you want to remove, down to the fitting you want to keep. I find it's easier if you hold the saw blade with teeth pointing towards you.
Then use a screw driver as a chisel and with a hammer drive the screw driver between the glued parts. They will pop apart.
Now chisel the rest of the glued part.
Actually the parts/fittings are not glued but solvent welled.
This does work, I've done it many times to not only plastic pipe but also PVC electric conduit.
Dusty