Most people I've talked to, which is mostly nonvegans, think it is unethical to let cats outside because they will kill wild animals. This is a more hypocritical stance than the reverse (a vegan who lets their cat outside) if you understand veganism.
You're also throwing around the word forced. People force choices on their pets, children, and even fellow adults all the time, but there are different levels of force. Putting down food for a cat that gladly eats it is a far cry away from shoving something down their throat or leaving it out until they have no choice but to eat it. I'd argue that it's often very appropriate to make food choices for a cat you live with, if a cat begs for some lasagna or a donut you probably shouldn't give it to them.
Edit: Also when people talk about forcing cats onto a vegan diet you have to realize the alternative is forcing livestock to suffer serious trauma for their entire life and then die. It's not hard to see that one of these is a more serious abuse of our power over other animals.
That is pretty irrelevant. You purchasing the product signals a certain demand for it, that demand will help determine how much product is requested in the future, there is a cascading effect all the way up the supply chain. Sure an additional chicken might not be bred just because you purchased a chicken, it's way more abstract than that. Maybe if a hundred more chickens are bought then a hundred more chickens will be bred as replacements plus extra to account for growth and failed product (dead or sick chickens). And if you were one of the hundred people who purchased a chicken you can be seen as one hundredth responsible for at least a hundred chickens which is the same as being responsible for the 1+ chicken. Do you think if nobody purchased chickens that they would just keep stocking the shelves?