I don't understand how you can frame things in "choice" vs "non choice" and come to the conclusion that Emet-Selch is the one that is the one invested in non-consent. Note, this is not a "good" or "bad" aspect of Emet-Selch, it just literally is. Emet-Selch is actually huge on consent. (Just not informed consent.)

Let's actually break this down.

The Ascians do not actually rejoin Shards by shooting lasers at the populace in the aspect they are trying to tip the Shard towards. Their plans always involve working with the population of said Shard and the Source to achieve their ends. They also don't tend to literally lie outright--though they certainly lie by omission--instead offering their chosen target something that will serve the interests of both parties. We can see this in the Vauthry scene. Emet-Selch doesn't visit Vauthry's mother in the middle of the night, while she slumbers, to inject her with liquid sin eater. He instead approaches the family and speaks to them directly, explaining what he can offer then and what it will entail. Once they accept the devil's bargain, Emet-Selch then does what he says he would--probably with a sardonic curl to his lips as he once again finds the justification he wants in allowing the "half men" to be the agent of their own eventual demise.

Venat, on the other hand, lies to us pretty much constantly. She lies about the origins of Zodiark and Hydaelyn to us. She lies to us about how much power she has, what she is capable of accomplishing with that power. She allowed Hermes's lie to Emet-Selch and Hythlodeus to stand. She lies about what will happen when she assumes the guise of Hydaelyn to her followers. She did not tell us that we were shattered 14 parts of a greater whole to allow that to factor into the "choices" you say she gave us.

Zodiark was the work of elected officials after debate and struggle to save their star. Venat basically hijacked their work as a part of her own plan--a plan she didn't even share with her closest followers--and acted like the act of summoning Zodiark itself was some sort proof of moral deficiency. At best, she just kicked the can down the road 12K years for us to deal with. And if after all that, we couldn't? Well, she left her escape plan to the most isolationist society in the known world--thus practically ensuring the people that would be able to board her ark were limited at best--and the remaining six planets were shit out of luck. Looks like she valued their lives in the worst case scenario about as much as the Ascians did.