Think the other way around. Imagine mankind would travel through space and would find a primitive reptile humanoid species.
What would we do? First we would try to trade and five them some useless things or some some knowledge to receive something valuable from them.
If they wouldn´t trade voluntary, and if we really need something special, then we would consider military actions or play gods for them, in order to force and enslave them, to deliver what we want.
If it would be planet that is suitable for humans, then we would consider to fight versus them, because they wouldn´t be able to defend their planet.
Well and if we need food and they are eatable, then we maybe would just turn them to animals, such as we do e.g. with cows and pigs and we would eat them.
And now think, how another species would act toward us humans. They would want our resources and labor power, they may want our planet and they may see us potential food.