Re: If you disagree with your instructor's explanations...
Using the Shu Ha Ri principles might help perhaps?
To my humble and probably rather shallow understanding, it's about taking everything in at the beginning. Both the good and the bad. Only after that you can deconstruct everything, analyse the parts that you've learnt and finally you can put everything back together the way you see fit. Create something new that is your own so to speak.
I'm only a beginner in aikido and I've agreed with almost everything that my sensei has taught us. After all he's been doing this for decades. Recently I've been back in my own country and trained in the closest dojo I could find. I didn't really care who taught me, I just wanted to train. Well they were really different and I wasn't used to their training methods. I was told off quite a lot in that first session although there were people who needed more help than me. Then I went there the second time and there was a different instructor. He is not remotely as experienced as my usual instructor but he was also a good teacher. I still got quite a few criticism but I learnt a lot of things from that one lesson as well. So I thought what if I opened up completely, forget the stuff that I've learnt while I'm in the dojo and adopt a complete shoshin (beginner's mind)? I tried that in my third visit and I did not get criticised at all as I copied what is taught as closely as possible while trying to drop what I learnt in my home dojo. In the end, I took in a lot more and of course I managed to understand techniques better as well when I think of the different ways of doing them. It's not that they're wrong outside of my home dojo, it's just different. And I'm still learning from them. Of course there are still things I don't agree with in the new dojo but I could just shed them later on and combine it with my own understanding to create my own aikido that is made for myself.
I also understand what you mean when you said that the instructor may have a very narrow understanding of budo and aikido. If it is that unbearable then perhaps politely talk to him after class to indicate that? If he or she is too arrogant to listen to your constructive criticism then I would suggest you move to another dojo.