There's a lot of variables here. I'm an engineer. At work I can say "I disagree. The reasons are..." and the reason my boss doesn't fire me? Because honesty matters in this context. Same for my marriage. If my wife says she wants to give the kids donuts for dinner, I can directly disagree because again honesty matters (to my wife, to the kids, to the marriage).

Since you didn't get too far into the specifics of who, where and why you might express disagreement in a lower stakes conversation I can only surmise.

You are at a bar and an acquaintance says "I thought Anyone But You was the best movie of 2023". What does that person hear if you simply respond "I disagree." Maybe that your opinions as a movie critics are more important than hearing their feelings? Why don't you instead just say "I didn't see it"? That would tell the person you generally don't watch rom coms and therefore probably wouldn't agree on what the best movie was anyway. Is honesty really critical here? Or is holding a conversation that doesn't turn people off the priority?

You are at work and your direct report turns in utter shit to you on a project that has some degree of importance. Do you says "This is unacceptable"? Or do you instead thank them for completing the task and then ask questions about the work, the product and them to see if they understood the assignment, or whatever else is going on with them or their work load?

Honesty is important in a lot of contexts. Bluntness is not the only way to express something. There are passive and indirect ways to be honest. And there are ways to honor other priorities while not being untruthful.

No one wants to be your friend, spouse or direct report if your knee jerk reaction appears to be a negative response to everything that's uttered.

Part of resolving this is tact. Just simply not uttering the first thing that comes to mind. Part of this is a reframe and simply prioritizing someone else's feelings over your own need to be honest or correct about something unsubstantial.