The fact is, FTL travel causes real, not just apparent, violations of causality. (Unless you restrict the FTL travel in certain ways which are hard or impossible to justify given the assumptions of Special Relativity.)

Why is this true? I'll try to explain, using an example I posted a few days ago, which has been vetted by Real Physicist.

Imagine a spaceship leaving Earth at a large fraction of the speed of light. As we all know, according to relativity, the spaceship experiences 'time dilation'; that is, to observers on Earth, the spaceships clocks seem to run slow, say by a factor of 2-1. So when a year has passed on Earth, the Earth astronomers will observe that the spaceship's clocks say only six months have passed. Remember, this effect is real; is will appear even after correcting for propagation delays caused by the finite speed of light.

But according to relativity, the spaceship's reference frame is just as valid as Earth's. In the ship's frame, the ship is standing still, and Earth is travelling away from them at a large fraction of lightspeed. So the ship observers will observe Earth's clocks as slowed by the same factor of 2-1. Again, this is a real effect (to the extent that the word 'real' has any meaning)not an illusion caused by the finite speed of light.

How can the ships clocks and the Earths clocks run slower than each other? This is one of the paradoxes of relativity, and I can't really explain it myself. But if you do the math, that's the result you get. Due to the finite speed of light, we never get causality violation in this situation. But what if we can communicate, or teleport, faster than the speed of light? For ease of argument, let's suppose we have an instantaneous communicator, an 'ansible'.

Now, a year after the spaceship leaves Earth, Mission Control fires up their ansible and sends an instantaneous message to the spaceship.

'Hi, how are you?'

Due to time dilation, the message arrives after six months have passed on the ship. The ship uses their ansible to reply instantaneously. 'Were fine, how are you?'

But according to the ship's observers, only three months have passed on Earth in the six months they've been in space. So the ship's reply arrives three months after the ship leaves Earth.

The reply arrives nine months before the message was sent!

I hope this made some sense. The problem is that the ship and the Earth have different definitions of what 'instantaneous' is. With a little more work, you can get the same paradox if you just travel faster than light, say at twice lightspeed.