My ex-colleague was terminated because of the internal politics in our company.
Is it a bad reputation for him to be terminated because of internal politics? How to explain to his future interviewer? Can he explain the details of what happened to him?
Absolutely, he can't lie to his future interviewer that he is still employed.
It is best not to lie. It is also best to be able to say what he learned from this experience. He should have learned that no one can afford not to play politics (or play them badly) in a company.Sometimes though the politics are at such a high level that you never had the chance to affect the outcome (luckily these issues often result in layoffs not firing). It pays to understand how good your boss is at playing politics as well as yourself. If he is bad, that is a signal that you need to develop allies outside your own group and/or transfer to a group with more political power.
In presenting it, he needs to keep the political discussion relatively neutral. More of an "I got caught between forces beyond my control" not "I am so angry at how unfairly I was treated by these jerks who fired me for no good reason." Without knowing the exact details of what happened, it is hard to give more than generalized advice about what to say.
Given the lack of details, it's hard to give a more specific answer because it can be ranging from 'tried to played politics, sucked badly, fired back' to 'was pushed out by someone manipulative'. Also, there's usually more behind the 'just internal politics'.
Is it a bad reputation for him to be terminated because of internal politics?
I'd probably not focus on the politics bit on the interview unless pressed really hard. Some might see it as a red flag because not everyone likes people involved in the politics or various other reasons.
How to explain to his future interviewer?
Something neutral as suggested by HLGEM such as "I got caught between forces beyond my control" will be enough, usually.
Can he explain the details of what happened to him?
There's no need to get into details because you might get too emotional, interviewer can misinterpret that, etc.
So don't lie, obviously, but there's very little point getting into too many details as it will not benefit you.
