Most good grammar books advise students, “Don’t use stative verbs in the present progressive.” For example, one shouldn’t say, I am knowing the truth but rather I know the truth. The verb know is stative because it indicates a long-term condition, not a discrete action. The same holds true for ordinary uses of agree, hear, hate, love, think, and want and many other verbs.
However, your students may pose counter-cases. What about I’m agreeing with you or—even more colloquially—a fast-food ad that claims I’m loving it? First, let’s acknowledge that rules about verb usage are really more like guidelines. If discourse conditions require language to shift, it will shift. Few people would call foul on I’m agreeing with you. It means “I am saying something that shows agreement” and is clearly distinct from I agree with you (“In general or over the long term, I have an opinion similar to yours”).
In the fast-food ads I’m loving it draws attention to the speaker’s being in an enjoyable moment, not in a long-term state of enjoyment. The intended meaning is “I have my burger and this moment is great.” Similarly, if I whisper to a colleague at a meeting I’m hating this, I want to say that things are temporarily unpleasant, but this too will pass. In I’m thinking blue for that wall, I’m trying to say, “My current thoughts are that blue would be a good color, but I might think differently later.”
So if a student asks about such apparent exceptions, focus on the temporary aspect of the discourse situation.