Even if our behaviour is entirely predictable it is not unreasonable to hold us accountable for our actions.
In fact an understanding of how our response to an action will change the likelihood of similar or related actions in future is essential in order to justify any adverse or punitive response at all. So only a predictable being is responsible in that sense.
The only situation in which determinism undermines responsibility or accountability is in the case where there is nothing that can be done to reduce the likelihood of future offensive behaviour. But most of us can indeed be manipulated, and it is only that lack of truly “free” will that justifies holding us accountable for our actions.
Source: (27) Alan Cooper’s answer to If we accept that (or perhaps given that) scientific investigation shows that there is no evidence to support the notion that human beings have free will, does it become unreasonable to be held accountable for one’s actions, if not why? – Quora