Hi mate,
Not anywhere in the Mahabharat or Ramcharitmanas is there a scene where rishis are eating meat. But yes, u were correct in saying that in Manu-smriti, it is said that rishis did eat meat... however i need to clarify a few things... so keep reading..
1. ahimsa is not just a budhist or jain idea... it is the second soul of the veda (after satya).. and budh and jain idealisms developed very well picking ahimsa to be there foundation from Sanatan dharm...
2.i like it that the manu-smirit did not rule out meating eat (i am veg...).. the reason i like it is because some people make comments saying that hindu dharma is very strict and u lose ur independce following it... this is utter rubbish... never once have the vedas declared that u should not do something... they only tell us that if we do it ... this will happen... NB. where orders have been given... read the whole chapter and u'll get to know that a guru ordered HIS shishya to do something AFTER the shishya asked for help....hindu dharma is as strict as u want it to be... the more u live naturally the higher up the ladder u'll go.. also.. this shows that hindu ideology accepts everyone... unlike others..
3. manu-smriti makes it very clear.. that eating meat allows for vices to come into u... eg. ur mind become unstable and animal-like.... so it says that a sresth vyakti i.e. an erudite being will not eat such things and be satvik aahari ... eat vegetables and fruits only...
4. not all aryans are rishis... u made a sweeping statement there... be very careful mate
5. certainly... there were some rishis... which i wouldnt call them rishis... who only performed yagnas and other activities for personal gain... a rishi doesnt do anything for personal gain...
I would advice u to read the bhagvad geeta... where bhagvan sri krushna tell arjun about the 8 qualities of a vipra/rishi.... after reading that u'll know that some of these were not rishis... ravan was right in injustfying the flaws of some of these people... but he was wrong in generalizing it.... Vashishta, Vishwamtra, Parashurama, Agastya and others are names of maharishis who have these qualities and did not do lowly acts