I know we're dealing with human aliens, but there is actually a thing called takotsubo cardiomyopathy, also known as "broken heart syndrome", where your heart weakens as a result of emotional trauma.
It is rarely fatal, but deaths have occurred as a result of it.
I don't think it would be up to us to decide if it is acceptable or not. We don't ask the cow if they think it's okay that we take their milk, their skin, their meat. Likewise, I doubt a more advanced alien species would bother asking for our permission if they decided they had a use for us.
On a more philosophical point though, there's also the matter of sentience. As far as we're aware the animals we use for food, labour, etc. don't have the mental capacity to really understand the situation they find themselves in. They can't process and understand the fact that they are being used. As we are a species that can, the chances that we'd let another species, even one more advanced than us, exploit us without resisting are probably pretty low.