And that liberals would stop saying that the media does not have a liberal bias.
The word “media” is plural.
Conservatives, please say:
The media have a liberal bias.
Liberals, please say:
The media do not have a liberal bias.
I am more annoyed with the conservatives that use “media” as a singular word. Conservatives should embrace prescriptivism.
I wish the medias stopped having biases.
Really? Do you have an agenda here?
If not, then justify why “agenda” is singular, but “media” cannot be.
Grammatically, the word “media” is a plural noun. The singular is “medium.” “Agenda” is a singular noun. The plural is “agendas.” There is a word “agendum” which refers to a single item on an agenda, but “agenda” itself is still singular.
The Latin word agenda, a gerund meaning " [a thing or things] to be done" is plural in Latin (agendum is the singular), but in English, “agenda” is singular.
The OP is correct. The word “media” gets misused as a singular all the time.
I would also like to take a moment to spit on the initialism, “MSM,” which is lame and implies a monolithic entity which doesn’t actually exist.
From dictionary.com; emphasis mine:
Yes, that usage is often seen. That doesn’t make it any less incorrect. I do not like the argument that enough people using a word incorrectly makes it ok. For example, I don’t care how many online dictionaries say that it’s ok to use “literally” as an intensifier. It’s not an intensifier and people who use it that way are subliterate and that’s all there is to it.
Part of the problem is that if you say, “The medium has a liberal bias”, then folks will tell you to go to a conservative seer. 
The Media ARE the Message.
We don’t view them as a monolithic entity. We view them as a lot of like-minded individuals who habitually engage in groupthink.
The media are literally biased?
i can has bias?
NO. Media can has bias. Do try to keep up.
Media can have bias. Medium can has bias.
Do I need to draw you a flowchart?
These are good news
Yes. 
That was likely true a long time ago, but it is not today. Most dictionaries, mine included, cite media as being both a plural AND a single noun, and the single noun has a number of definitions.
The OP is wrong. Every decent dictionary cites “media” as both singular and plural, depending on the definition in use. In the context the OP is complaining about - the mass of communications outlets including television, radio, and regular print - it is a singular noun and has been used that way for quite a long time.
Collective nouns are perfectly acceptable in English, and are grammatically treated as singulars in American (and Canadian) English, as you, an American, should know. If you are like 99.999% of your countrymen, you very likely say “the data leads me to this conclusion,” treating it as a singular, not “the data lead me to this conclusion,” even though data was originally a plural in Latin. “Stamina” is another example; that used to be a plural, too. “Data” has now taken on the sense of a collective singular. “Media” is like that now. In some contexts.
We’re speaking English, not Latin. Nothing wrong with changing some words to suit our uses, and this isn’t a recent change.
By your standards around “media,” you’re contradicting yourself. Originally, “agenda” was a plural, “agendum” the singular, and “agendas” was not a word at all. “Agenda” became a singular simply because it makes sense to use it that way.
I agree that misuse doesn’t make something okay, but there’s a reason “media” has found purchase as a singular; it’s not illiteracy, it’s something done by a sort of design. Using “literally” as an intensifier is stupid because there’s just no reason to do it; it serves no purpose, and it probably won’t last (although it might; lots of words we use now have completely different meanings than they used to.) But “Media” as a singular to describe TV, radio et al. is quite useful as a collective noun. It had a distinct meaning apart from a simple plural of “medium.”
Do you approve of the signs at express checkout lines in supermarkets saying, “10 items or less”? Constant misuse does not make the misuse any less incorrect.
No: The medium is the message, according to McLuhan, so the media would be several different messages. Similarly, the media (in the US) have conservative biases.
(They aren’t all the same message, they each have different biases. If they all had the same message and the same bias, they would be the same medium.)
Part of the problem is, what word should replace “media” as a noun referring to everything that word does these days? I would argue that “medium” is clearly wrong for the job, so what’s left?
Ooh, the descriptivists are gonna jump all over you! Link.