because he founded the ITF which was well before WTF came along despite what others with their own agenda or lack of information might tell you.. it is also to do with politics since choi was based in north korea and WTF was founded by south koreans and everyone knows the animosity between those two.WTF dont regard him as founder of tkd and ITF do, itf is much different than wtf if you ever take the time to watch it.. itf has more hand techniques than wtf and is more complete martial art and not sport directed, ITF use " tul " patterns and WTF use " poomse " patterns or forms whatever you wish to call them... basically both use totally different forms and have different theory for certain techniques and names.ITF also makes use of a sine wave movement in almost all of their techniques .. its like an up down movement before executing a technique .. WTF does not make use of this sine wave at all..
WTF is mostly kicking ..ITF has a good mix of both kicking and hand technique...
WTF do not " hate " Choi but dislike him because they feel his status is not deserved as father of tkd... reality is though that choi founded itf about 10 years before WTF came along making claims ITF was not legit or real tkd .so whos wrong ? well depends who you ask.I believe ITF have it right.
certainly ITF is a more complete martial art , and yes to me both WTF and ITF are so different that they are different martial arts ...ITF even use different type way of spelling it .they spell it Taekwon-do, WTF say just taekwondo without the - before do.
if you ever watch WTF in sports sparring on tv u will see how clumsy it looks .. certainly the kicks are good but they never keep their hands guarding their face... hands down by sides all the time. what good is that ? now watch ITF you will see something different ... there is a mix of both hand and leg technique , and fighters guard their face at all times even when kicking...
ITF is a well formed martial art which choi spent years planning and developing, many techniques are based on on law of physics.. it is very scientific.also inspired by great martial arts like shotokan karate and taekyon and hapkido, but certainly unique and different.
WTF just tried to copy some old korean kicking styles and make something that looked a little different, less development went into it.
it really is difference of opinion and ignorance by some.
WTF just think theres is the best and real tkd even though they were founded in the 60s about 10 years after itf , they were inspired by choi but then ego took over.
Choi is regarded by most tkd practitioners in the world as founder of tkd, so wtf have a problem with him because they are jealous of his status.
i hope this helps .