Animals are sentient (like humans) so we should treat them like humans and not exploit (eat) them.

Let's put this in logical form:

P1. Animals are sentient like humans
P2. We don't exploit humans by eating them
C. Therefore, we shouldn't exploit animals by eating them

Is it valid? No. Even if we grant both premises, it doesn't warrant the conclusion. Just because two things are alike in one way, doesn't make them equal. But what if we changed it up a bit...

P1. Animals are sentient beings.
P2. We shouldn't eat sentient beings.
C. Therefore, we shouldn't eat animals.

Now we have a valid argument in that, if we grant both premises we have to accept the conclusion. But this argument can never be objectively sound because we have a highly subjective premise (p2) and a (currently) non-falsifiable premise (p1). People's difference systems of morality will dictate if they agree with premise #2 or not.

This argument is loaded with several value claims—claims that are neither right or wrong but opinion or values. If I were arguing on behalf of the vegan, I might rephrase this argument using conditionals:

P1. Science overwhelmingly supports the idea that many non-human animals (including the ones we eat) are sentient.
P2. If you agree that sentience is the measure by which we should grant beings certain rights including the right not to be slaughtered for food, then
C. You must agree that we shouldn't eat animals.

This is a more convincing and reasonable argument, IMO. The major difference is, were not trying to trap people with bad logic; rather, we are allowing them the option of disagreeing with our condition that warrants the conclusion.