If you pick Red, destroy, synthetic life has no choice to live. They are all wiped out.
If you pick Green, synthesis, people have no choice in having their DNA rewritten.
If you pick Control, people have no choice but to accept the Reapers.
Any action Shepard does impacts the entire Galaxy. If the entire Galaxy wants to become a new type of life or wants to have the Reapers controlled it doesn't matter if Shepard wants to Destroy them (and all synthetic life). Only Shepard has a say in the matter