Transphobia is just what it sounds like: An irrational fear of transgender people and ideas.
Not everyone who is pro-binary is transphobic, only those who are also senseless afraid. Some popular examples of transphobia are believing that trans people are pedophiles or that we will sneak into women's lockerrooms. An example of a pro-binary person who is not transphobic is a parent of a trans child who doesn't want their child acting like the opposite sex because they stop accepting anything less; this is pro-binary and unwise, but it is a completely rational thought.
Trans & Gender 101 >