I think there's a subtle mistake in the rationale here, which is to equate the effect (Darwinian self-interest) with the cause (that, therefore, the behaviour itself must have been performed cynically).

Just because the outcome of a certain behaviour is to favour the interest of the gene, you cannot generalise that the motivation behind the behaviour intended this outcome; indeed, as you have pointed out before, humans have very low self-awareness.

When it comes to the evolution of behaviour, the only thing upon which selection acts is the outcome of the behaviour – it does not care about the mechanisms which lead to that outcome. In the case of human behaviour, those mechanisms involve neural processes – thoughts, emotions, etc – which depend upon the development of the brain, including memories, personality, preferences etc. It is not necessary for the motivation of the human to be cynical in order for the outcome – the level at which evolution acts – to have the effect of promoting the interest of the set of genes responsible for the behaviour.

It is entirely plausible – from the perspective of natural selection – for people to altruistically care about other people enough to give charitably and anonymously because they simply care about the cause to which they are giving. As an example, many people donate to Cancer Research because they lost a loved one to cancer, and they don't want other people to experience that same pain – the behaviour is caused as a side-effect of empathy, not cynicism (empathy itself having likely evolved under the selective pressures of our early social environment). Of course, the outcome of this behaviour may well provide social benefits to the individual responsible, as you highlight, or may even be viewed through the lens of "curing cancer would be in the best interests of the individual's family and gene line", but this is making the mistake of interpreting the mechanisms of a behaviour – the individual's motivations – through the lens of the outcomes of that behaviour.

I would say, therefore, that to generalise a cynical interpretation onto the motivations of all humans is to oversimplify the reality, which is that a great many different textures of minds, and a great many different motivations – some noble, some selfish – add up to the complex outcomes which have created human civilisation. Your mind and motivations may be cynical, but that does not mean that everyone else's must be as well.