Attempting (and in cases, succeeding) to ruin another's chances of winning a title, whether in the same team or not, comes from the same way of thinking. 
totally different situation 8ball is asking what Senna would do in Alonso's shoes. for if you want to use a mentality alone then that could be said for many different rivalries in the past
besides you use the word ruin anothers chances where does this apply for the lewis alonso rivalry?
and please dont make me have to rehash the senna prost incident and why Senna did what he didl...
ive been on this forum long enough but back in time somewhere on here is my thoughts on the matter by all means look it up.
Winning at all costs is the mentality, and it doesn't matter whether it's your team-mate you're taking out or a driver from a rival team. If the people who had done the latter wanted to win that much and had a team-mate that was threatening their status, I'm willing to bet they'd give it some thought.
And when I say ruin someone's chances, I mean make it so that their championship is under threat and that, because of your actions, they may lose it.