[DoodleDawg]

Then why aren’t they taxing planned Parenthood?

For the same reason why nobody taxes the NRA. Legally it's a non-profit organization.

[justme4now]

But you said:
“Unlike corporations the NRA is a non-profit. Accepting federal funding would probably change that and open them for being taxed.”

Planned Parenthood might be a non-profit but gets Government money every year!