I like resistance, to a point. Resistance allows me to find the weaknesses in my technique and work on them. If someone keeps poking me in the ribs, it's probably because I'm not moving correctly, or my posture is off, or there's too much tension in my technique.
I've been to dojo's where all I have to do is touch uke and they fall down, that doesn't teach me anything.
That being said, the person in the most danger of resistance is the one resisting. A skilled nage will change technique because that's what uke is asking for. An unskilled nage will try to force the technique and may injure uke. Uke should resist enough to help teach nage, if it turns into a test of strength, or a contest of who's more macho and can take the most pain, someone will get injured.