This point is far larger and deeper than just political debates, which is where I’ve generally employed it: you might be wrong. Your knowledge might be incomplete and your perspective colored by history or feeling. Your assumptions might not be valid.
In politics this attitude should prompt a careful review of what others are saying about an issue. You should repeatedly reach out and try to understand what other people think and why. If you find yourself dismissing their ideas, or attributing feelings and motivations (anti-Americanism, racism, transphobia, etc.) which they do not recognize you’re on dangerous ground.
We will always have disagreements. Sometimes the fact sets and the values of different actors are simply too disparate. Often the differences arise out of hopes and predictions about the future… elements about which no one has perfect knowledge. Nevertheless, you should disagree with people on their terms. You should be able to restate their ideas in a way which seems fair to them and you should (in the absence of compelling reasons to do otherwise) never doubt their motivations or reasons for holding certain positions. Transphobes will be open about transphobia. It is epistemically risky to hear people talk about fairness in women’s sports or social contagion among teen girls and chalk those ideas up to transphobia. What if they’re actually worried about fairness in women’s sports and social contagion?
The truth is that most people won’t credit the ideas or motivations of people they disagree with because it’s neater and emotionally more satisfying to dismiss their positions as simply hatred or bigotry or ignorance. When you encounter this tendency you will find it almost impossible to get people to listen… it’s like there’s a reflex protecting their worldviews, and any effort to open the lids of their ideological boxes (or open the doors of their own ‘locked rooms’) occasions hostility and emotional reaction.
But this is not limited to politics. The tendency starts and develops in inter-personal relationships. People always feel that they’re justified, and those who they perceive as competitors or offenders or antagonists are unreasonable or malign. It is extremely normal to attribute uncertain knowledge or negative motives to someone with whom you are in disagreement, or someone who you resent.
This is a PSA: for most (not all) conflicts the solution is not certainty and resentment, but humility and communication. Sometimes you will encounter people who are trying to hurt or undermine you (beyond the petty insults and jealousies which are fairly normal, especially in unhealthy relationships). For those malefactors the best strategy is hard boundaries, or going ‘NC’ (no contact). However, most of the time there is simply a difference of perspective, and the gaps can be closed (somewhat) through earnest and friendly communication.
If someone really does wish you harm or really is a bigot or really does have covert designs they will eventually make this clear to you-no guesswork or attribution should be necessary. For everyone else, listen with an open mind. Policies apply to the entire society, after all-they’re not anyone’s private preserve. We all have to live next to each other. We can each choose the path of indignation and suspicion and hostility… or open-mindedness and graciousness. If you’ve never tried the second set of options in a concerted and systematic fashion I recommend that you do. The results might surprise you, and your efforts will go a tiny way towards healing the world.