Bullshit indeed as the Prime Directive has nothing to do with the right to live.Oh BS.
We (not all of us, some among are less savage and don't) eat monkeys, pigs, dogs and cows, all intelligent, sensitive and social mammals. So much about how fantastic our natural morals are and how totally unnecessary culture and ethics are.
Meat-eating which has been an essential protein source that made our brains grow now endangers our life due to climate gas emissions and inefficiency compared to normal food (we all know the 1:10 ratio). So it is absolutely necessary that we force ourselves to stop with this totally natural behaviour which is deeply ingrained into us as we have done it for tens of thousands of years. In order to achieve this goal we we need very counterintuitive and radical animal rights that forbid us to eat meat.
Back to Trek, if pre-Fed humankind or the UFP would follow their guts and help everybody they meet without thinking about the consequences they could harm a species like Menk at the cost of the group they help, they could liberate a world occupied by the Klingons and get drawn into a war of galactic proportions or they could help a child which seems to be tortured by her mother whereas she does in fact merely wean it from a particular gas it needs at early life (Broken Bow).