aikido perspective: I'm inclined to listen to Ueshiba, Takeda, Sagawa and Shioda over some random instructor.
fighting perspective: I"m not sure it's the right thing to be asking aikidoka about fighting, but I think the concerns are overblown. As I said, I don't recall seeing MMA fighters or judoka going out of their way to protect their fingers and I don't recall a fight being stopped because a guy broke a finger and couldn't continue. It's just a finger, rub some dirt on it.
You can listen to whoever you want, I'm not telling anyone what to do, just sharing thoughts and engaging in discussion. I'm also not inclined to listen to random posters that can't maintain civil discourse. But I can respond politely anyway.
You do in fact see MMA fighters break fingers fairly often. This is even with some support from their gloves and tape jobs. And it does affect their overall performance. They don't generally quit because of it (unless the doctor makes them), but it does affect them. I like the "rub some dirt on it" direction, I use that myself. However, if you can avoid it through training methods, why not.
As far as asking aikidoka about fighting goes, that depends on the focus of your training. If you do Aikido for health or other reasons, don't worry about it. But if you have any expectation at all that what you are learning could be useful in a self defense situation, then you should think about these things. Again this is an individual choice, choose however you want.