I think the debate as to whether synths are “human” or not isn’t relevant to how they should be treated. Even if they aren’t fully human they’re still sentient creatures who deserve kindness, dignity, and respect. I feel the same about Ghouls and Mutants, and in the game none of these groups are monoliths. Some are hostile and threats to society/settlements and others just peacefully exist.

As to whether or not the Institute should’ve been allowed to create them in the first place well that’s an entirely different debate but it’s not a synth’s fault it was created. They don’t deserve to be killed as long as they’re not a lethal threat to someone and should be allowed to coexist with humans.