This argument, as far as I know, relies on the nature of time dilation. You see as your velocity increases closer and closer to the speed of light, time itself begins to slow down. This is not an analogy or some fancy math trick, this is a real thing you can measure in the lab. As you get closer and closer to the speed of light time slows more and more. Such that as you reach the speed of light (again this is physically impossible at least for anything with mass) you can think of time as stopping. So for light or anything that moves at the speed of light they’re kind of isn’t such a thing as time, but I digress.
So (again even though it’s actually impossible), what happens as you start to go faster than light? Does this trend continue? If it does that would mean that time starts to reverse. And once you see that faster than light travel might imply time reversal, it should be easier to understand how this would violate causality. Because how do you get event A caused by event B when event B was before even A?