Driving your car at full throttle once you get up to speed slowly is not bad for the car or engine.
However if you just full throttle the cars engine right after you get into the car and are not already up to speed then it can be bad for the engine.
For example if you are sitting at a stop sign or just sitting still and then you just floor the gas pedal and rev the engine right up then that can be bad for the engine.
But once you're already up to speed on the highway or road then full throttling the engine is not bad.
However you should never speed unless you're on a race track or closed course because you can get killed or kill someone else as well.