This is old news. They have been planning this for quite some time. The government first announced that they will be ending the tax benefits for Bitcoin sometime during mid-2018. As a first step, they had made cryptocurrency exchanges ineligible for the income and corporate tax deductions, which are provided to small and medium-sized enterprises.
I thought they already legalized the market and all the exchanges are functioning as per the rules and regulation set by the government and they could spend bitcoin in stores.
This was a major blow to many of the exchanges. For example, Bithumb paid 27.2 billion won as corporate tax on its net profit of 250 billion won during 2017-18. Under new rules, they are liable to pay almost double that amount (close to 54 billion won). For the past several years, the finance minister (Hong Nam-ki) had adopted a hostile stance towards cryptocurrency and I don't expect it to change anytime soon.
Does the government having a hostile attitude and extra tax for the crypto exchanges or are they collecting the tax as per the normal standard in Korea, if they are only collecting the normal tax slab you cannot call it a hostile attitude as you cannot exempt one sector and collect the same tax from other sectors as it will create further issues.
No, the South Korean market was never fully legalized I remember. They gave ICO's and exchanges the chance to operate there and didn't ban them from running their companies, but it was always in a grey spot, and I am assuming that this move is going to tip them over the edge and make it fully legalised.
Not hostile at all to be honest. It was never fair for crypto businesses to get away with paying less tax and it might have been a good strategy because people where definitely more interested in running crypto companies since the government was more lenient on them, but now it's time to face reality and pay up to the government.