It is always tempting, you are desperate to justify yourself in an interview.
And the best way to do that is to demonstrate what an idiot your previous boss was. Or how incompetent the board was. Or what a ridiculous strategy they were following.
It is probably one of the most common mistakes that jobseekers make. It is entirely understandable and completely wrong. All employers want loyal committed and preferably compliant recruits. It is best not to fall at the first hurdle by giving them definitive proof that you are anything but.
However idiotic or stupid your employer may be, and we all concede that it is quite possible, do not fall into this basic trap. You will almost certainly head to Room 101 before you get a further chance to explain yourself.
All employers have their own agendas, few of them are perfect and everyone accepts that. But few accept that the person you were reporting into is more idiotic than you. So if you’ve been stupid enough to work for them that any length of time it reflects badly on you as much as it does on them. And your disloyalty and disrespect will put almost everybody off.
By all means explain you have had disagreements, by all means explain that you were not the right person for the job. But never be rude about a previous employer, because you won’t get the next job.