I had no problems until now with this... but did not had any agressive neightbour... For agressive civilizations meeting a new civ is meeting a new enemy for conquest, i don't see a problem with it, getting every civ to behave the same way (being friendly or neutral until have problems with you) for me would be the problem.
And it is even logical, having only you and him in the continent, if he is a warmonger it is a very good chance to have all the continent for him without the worry of being backstabed while doing it... it is what i would do if i begin a game willing to conquest the world...