Not wishing to be argumentative but it's reading individual bits that is the problem with RMW. Imagine that the bit we want to write to has a capacitive load. To write to a bit (using PORT) the PIC reads all 8 bits, modifies the specified bit and writes back. If we now write to another bit but the load has prevented the original bit from changing, the PIC reads all 8 bits (getting a wrong value from our original bit), modifies and writes back. That why the problem is called Read Modify Write. There are 2 ways to overcome this, either buffer in software or use LAT, both of which "remember" what value was last written.