Me - I do that sometimes.
You - In fact, you just admitted to be one of those selfish drivers who
often speed up to prevent others from changing lane.
Epic. You read what you want to read, invents and project your imagination as fact.
I said I speed up to close a gap so that vehicles are not tempted to cut in abruptly. Not tempted = not yet done so. But you came up with your narrative and make it seem as if I will speed up if a vehicle forces it's way into my lane.
Defensive mean to discourage or reduce the possibility of something from happening. But if as you described a vehicle had forced itself into my lane, I would as a matter of safety do the necessary to avoid a collision. Did I say that I will defensively accelerate and bump him off the road? Tsk tsk tsk. Don't come up with scenarios that don't reflect what I said.
If people lane change without checking or force their way into your lane, the correct and defensive way is to apply brake, slow down your vehicle and allow the other vehicle to lane change safely.