Are you implying that rejection of subjectivity is the source of atheism of all stripes?It's not the case that they accept subjectivity. You have to get into the details of it, because they will simply define subjectivity differently, and all words associated to it. So they say, I accept subjectivity, by which they mean that opinions are a function of the uniqueness of the brain. In extremes they then might go into racism, as that different races have different opinions, but usually they will go into the complexity of the brain, how there are trillions of possible configurations, implying that the uniqueness of the configuration is what makes for opinions.
'Subjectivity' is a term that comes from Wilhelm Friedrich Hegel that has a belief system where human thought is the manifestation of God, and Hegel uses his philosophical system as a tool to deal with the seeming contradiction of the death of Christ. In other words, Hegel was searching for a tool to make the concept of the 'Death of God' OK. At the same time he believed in an ontological proof of God. It appears he did not accept your concept of subjectivity since he believed in ontological proofs, yet he is the person who defined 'Subjectivity', the term. When you use this term you bring Hegel with it which imposes that different points of view are simply different aspects of God, so that the death of Jesus (God to him) is not the death of God but the death of death. (Going by the Wikipedia article on Hegel). So his subjectivity is that God is something that is being manifested in our thoughts and seeming contradictions about God are merely different aspects of the same God. This would not even occur to an agnostic as they are doubting the existence of God not the nature of questions about God.
That being said an agnostic has a different idea about subjectivity from Hegel, as they are not dealing with the contradiction of Jesus death upon the cross. (I'm not certain that this is the same subjectivity to you either.) For them subjectivity seems to be something much simpler, merely that not everything is understood by everyone in the same way. They may not even think about the inner workings of the brain. One person once said to me that they thought truth was a diamond with many facets and that we can't see all the facets at one time. They didn't mention brains or psychology at all but were talking about experiences. So when you say 'Subjectivity' it is not always clear which subjectivity you mean.