That's understandable. It is bad form to instruct your seniors -- and also a bad idea, because you're probably not as right as you think you are No matter how wrong you think he is, you really will do better to just bite your tongue, let him practice, and leave the instruction up to your sensei. If nothing else, it will probably save you an embarrassing incident down the line when you presume to "instruct" someone who is much senior to you.
"When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. But when I got to be 21, I was astonished at how much the old man had learned in seven years." -- Mark Twain
Honestly, I think that's the root of a lot of problems in Aikido and I'm done with that - if I think someone's wrong I tell them. If they're actually right they should be able to explain why in a reasonable manner. If they can't then...something wrong.