Laser pointers are easy to get and point at helicopters and airplanes.

The FBI successfully arrests and prosecutes those who do. Why would this be any different?

https://www.fbi.gov/newyork/press-releases/2014/westchester-...

I'd imagine if this became a critical piece of our infrastructure the FCC or some other government organization would step in and make products that interfered with them very difficult to obtain.

Not to mention I could have a rifle by the end of the day in my state.

Are they? A decent rifle is not difficult to obtain or use. There are many places you can practice. You don't need to be that accurate to be extremely dangerous and pull off an attack like that.

Meanwhile lidar spoofing attacks are likely going to be far harder. You need to obtain expensive (and probably illegal) equipment, and have the technical knowledge to use it. I don't know what the range of such an attack would be, but I don't think it would be better than a rifle.