It's quite a bit more nuanced than that, unfortunately.
For one, purveyors of bullshit often get pretty good at hiding the fact that they lack solid sources for their information. Furthermore, for many politically controversial topics, it's quite easy to find authoritative sources to support any point of view. Climate change is a good example here: the scientific community has a near-unanimous consensus that global warming is happening, that it's primarily human-caused, and that its effects will be nasty. But it's not at all hard to find authoritative-sounding articles claiming otherwise, sometimes even from people with solid credentials who cite peer-reviewed research.
Sometimes there are very clear indications that something is bullshit, such as claiming a scientific result for non-scientific concepts (e.g. vital or life energy). Sometimes it's a topic I already know quite a lot about and have learned to notice the ridiculous claims from a mile away.
The really tricky situations, though, are when reading about something I know very little about. In those cases, I find it pays to first of all read different viewpoints. I first of all want to hear the viewpoints of relevant experts or people directly impacted by the topic. For example, if I want to learn about what fiscal stimulus means for the economy, I'm going to look up the opinions of different economists, primarily through blogs and op-eds (direct academic research is often too dense to be useful for somebody new to a field). Then the question becomes: how do I decide who is right? For the economics example, I'd want to look at who is using data to inform their opinions, and whether they are using sensible models to inform their conclusions. For other situations, such as racism, I'd want to look at who is paying attention to the people specifically impacted by racism, including a combination of empirical data and personal stories by those impacted.
Very often, the answers to these sorts of controversial political opinions are not at all easy to suss out by somebody who is ignorant of the relevant information. It's easy to write an article that will fool people who don't know other data that contradicts the article. That's why learning how to detect bullshit is really important.