一个问题关于People who like it,love it.People who don't like it,ha

一个问题关于People who like it,love it.People who don't like it,hate it.
这句话：People who like it,love it.People who don't like it,hate it.出自一本外文杂志,先问一下为什么who后面加的是like(动词原形)而不是likes(三单)?
这个who like it/who don't like it,跟在who后面做的是甚么成分呢?