The can voice their opinions, and we can voice our opinion of their opinion. Freedom of Speech has never been freedom from criticism. Saying that people should be allowed to post racist comments but people can't call them out on it, is what's hypocritical.
If you are talking about banning people for posting racist or homophobic opinions, sites have the right to ban you for not following rules. Freedom of Speech only protects you from legal action, private organizations can shut you up anytime they want. Many sites don't allow racism and such due to the shitstorms they cause. Not only that, but the speech allowed in sites reflect the site itself. If you were to allow racism in KYM, it would send the message that KYM has no problem with racism.
But in no case is banning people based on their opinion discrimination. Treating people differently based on status outside the individuals control is not the same as treating people differently based on what they choose to believe. If someone chooses to be an asshole, it's not discrimination to treat them like an asshole, and if someone is racist, it's not discrimination to treat them like a racist.