Humans have free will. If there is no free will, then moral language would be meaningless. Without free will, there would be no moral responsibility. And without moral responsibility, there is no civilization. To deny free will is to reduce man to a complex machine with mere animal instinct. If all we have are animal instincts, then the strongest instinct would always win, but that's not always the case. We can choose the lower instinct over the higher one. Outside forces may be influencing, but never determining.
If we look at any event of the past or present, we can see how prior events lead to their inevitable conclusion. Thing is, the same will be true in the distant future. This means that present and future events are also inevitable.
One example I like to use is crossroads. It appears like you have a choice of which direction you can take. Problem is, only one road will lead you to were you want to go. That means the other roads were never an option. If they were never an option, then you never had a real choice, just the illusion of it.
Some may claim that this means that people should not be held accountable for their actions because their actions were inevitable and out of their control. Problem with that is, if you have no choice in committing a crime, then you must believe that the jury has no choice in convicting you of that crime.