dust on new lens: should i send it back?

Seems like you bought yourself a showroom/secondhand...
I bought a new nifty fifty too with simelar amouts of dust on it.
if you buy something new, you expect it to be new.
So I brought it back

Is the dust ON it or IN it? That makes a big difference. If it's on it, that's to be expected - give it a blow with a rocket blower. If it's in it, well, the nifty is prone to having that happen, and unless it's a huge amount it won't affect your images.

Canon doesn't send its lenses to retailers in sterilised, airtight bags. Dust is a fact of life.

I'd only consider if it there is a truly ridiculous amount of dust INSIDE the lens. Can't tell from your photo alone.

Wow.. where did you get it from? I'd bring it back.

believe me, all the dust is inside. each 'spot' is a dust speck. came from b&h.

Was there any sign of usage? But you should exchange for another one anyways.

I'd expect a nice clean lens, even for a nifty-50. Send it back before the two seeks and exchange it.

other than the dust it's immaculate.