Yes, the title is provocative, the actual subject here is to say that whether we have free will or not changes nothing about how we life our lives.
Case for free will
I would say that human beings live life with the perception that we have free will. We tend to cite our ability to make seemingly arbitrary decisions as the primary evidence for this. As we can cite no strong causal source for our decision, it seems to us to come from a kind of self determination rather than determination from outside of self.
Those arguing for determinism would point out that the notion of self is something of an illusion since all of us are composed of the same matter as everything else, and that for the most part the physical universe seems determinate. Very accurate predictions of cause and effect can be observed. There is also little direct evidence for some irreducible agency for that free will. In rebuttal to the arbitrary decisions, it is pointed out that just because the causality is not known, does not mean it is not there. Plausible explanations for any given choice can be postulated. And indeed many can predict or influence what are thought to be arbitrary decisions with great accuracy, calling into question our perception that they are actually arbitrary.
And of course there are theological arguments on both sides as well, though by and large free will dominates in most religions.
But who cares?
If we postulate the two possible states and the meaning it would have for any practical action we could hope to take, you quickly come to discover it makes little if any practical difference.
If the person who favors free will, were to be convinced there was no free will, then whatever opinion they now have, or action they now take, was predetermined anyhow. The revelation itself was part of deterministic outcome. You can't choose to stop making choices because that would be an act of will, you either will or you won't.
If a person who favors determinism is convinced of free will, then they had always had the choice of action even if they felt it was fate. Whatever destiny they thought favored them was none the less the product of thinking there was destiny and the agency of having it, thus there is no reason for them to change course upon the revelation. They were self determined before, and they remain self determined now. If they had tried to not make choices and exercise their will, then even that itself was an act of choice you were acting on.
If you think you have free will but you are wrong, well id doesn't matter since you don't actually have a choice whether to think you have free will or not.
If you think the world is determinate and you are wrong, well you are still making decisions and acting thus exercising your free will even though you assume its predetermined since you are unable to know what the future actually holds.
Even if you un-stick in time, its still pointless.
If there is free will you can't see the future since its not known in the present, you can only fudge along with your best guess as to the outcome of your actions.
If there is no free will you can see in the future but can do nothing about it and must trudge along on the predetermined path to meet the pre-determined outcome.
Your challenge... Prove it matters in the slightest if we have free will by illustrating the practical difference in outcomes for a person acting in the same situation under one assumption and the other.