I believe the title already gives a pretty good TLDR, but let me provide a little extra context.
I play in a group with two clerics, a rogue, a fighter and a bard (me). It's also important to know that the DM is a player in one of my groups and plays pretty much exclusively lawful good or neutral good characters. I am on good terms with all of the people involved and I don't intend to change this. We're all adults and if this ever gets out of hand I'm sure we'll find a way to talk things out.
Now to the ingame problem. My character started out chaotic good with a pretty strong emphasis on the chaotic part. She's a fey and orderly things go against her very nature. It's usually small things like planting flowers in the middle of the streets or "resorting" some shop shelves. However, due to some not so nice things going on in the world right now, she began shifting a little more towards the neutral side by developing a indifference towards the lives of several faction members in the world (mostly cultists of various evilish cults).
This led to the party steamrolling a bunch of cultists who expected us to pay a toll for crossing their lands with my character hypnotising them beforehand.
Another encounter had our rogue grow tired of a spectator who blocked our way with obvious implications of combat should we ignore him. Our rogue decided to backstab the spectator mid conversation.
I as a player don't really consider these acts evil. Neither does my character. But apparently the DM and at least one of the clerics see things differently. Which in and of itself is not a problem. However, I got wind that they plan to invoke some sort of plot to "make the party repent for their evil ways". And that's where my issue arises. I have no problem with players or characters who want to be a shining example in an evil world and who see the good in everyone. But I have zero interest in playing such a character and it feels like that is what this amounts to.
So, I'll do the obvious thing and talk to everyone involved before the next session. And that's where you come into play. How would I go about this? What arguments might help my point and what am I missing? If shit hits the fan, I am ok with leaving the game and I know that they will accept my decision. But I prefer to avoid this, as I really enjoy the campaign and my characters role in it and in the group.
Golden rule: Everyone should be supporting the player group having a rewarding experience. That's what it's all in service of.
The players can say "that's what my character would do," just like the DM can say "well it's realistic that the bugbears would set an ambush and come out and outnumber and kill you all," but neither is going to lead to an enjoyable outcome.
I have no idea what to recommend, for the details of what you or your group should do in this exact situation. As you said you're all adults and it's ultimately up to all of y'all however it works out. But the overall principle of keeping an eye on, yes we have our individual characters and we're trying to develop and express ourselves in character and sometimes tension between our incompatible motivations is a big part of that, but also, we're also all responsible for the whole thing ultimately working out well -- that's what I would recommend to keep an eye on (for you and for your expectations of what other PCs should be "supposed to" bring to the table in order to be fair to you + your character).