Yes but alonso has the advantage of using both fluently.
Exactly, JB's point is that he couldn't be sure alonso wasn't undermining him.
I can't quite work out whether he's saying it would simply be difficult for the newcomer or whether he thinks the incumbent would undermine the newcomer.
Nor whether he's implying he would do that.
Personally I think it's happened naturally at mclaren to some extent with JB being a nice guy but also deliberately doing 'team buildy' type things but crucially I don't think he's undermined Lewis, I think Lewis has done that himself.
However, you can imagine Lewis being insecure enough to wonder whether the other guy is mocking him to the team...wonder if any of that happened at McLaren.
I have been in situations before where I felt uncomfortable because I didn't know what I was supposed to do in order to curry favour whereas others were more manipulative/political/brown nosey.
I'm not saying Button is any of those things, simply that lewis may not have thought of taking out his mechanics for dinner etc (and I imagine that's mostly JB being a nice guy rather than purely political by the way) - he might have seen button building better relationships than he has despite being the newcomer and wondered why that was (hint, don't walk around MTC with sunglasses on and phone to ear all the time and leave twitter alone...!). He may have thought it was all down to performance and that was all there was to it.
Funny choice to go to mercedes and build a team if any of the above is remotely true mind, unless he's finally realised it but needed to start afresh to put his relationship building skills into action...!