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).

Are you and the rogue chaotic good, or chaotic neutral? It doesn’t seem like you’re clear on this with the rest of your party. Murder (e.g., backstab in the middle of dialogue) is not a “good” action, any way you slice it, even if the spectator is an asshole, evil, or through RP, would have eventually led to combat resulting in death anyways. If you were playing true chaotic, it’s understandable, but it doesn’t sound like that is what was made clear.

And if you’re trying to force an alignment shift, consider that you may be ruining the enjoyment of everyone else at the table; if I’m playing a lawful good cleric, I’m not sure my character would party with a true chaotic fey, which would essentially end the campaign.

This thread reminded me how much I despise when players play an alignment rather than just playing their character.

"Hurt durr, I'm a falafel, that means I have to be a dick to you, even if it makes no sense why our characters would keep working together if they are both so committed to opposing everything the other does"

I remind my players that this is a game first and we're here to all have fun. So if they aren't receptive to a chat one on one about how they are playing. Maybe they aren't a good fit.

If the DM is always allowing them to continue like that after a serious chat then I see no harm in moving on and finding a group that would be glad to have you.

In a real story if you had a group of thieves travelling with a paladin that hates theft, wouldn't you expect the group to kill him?

Going to echo the prior comment. But here's my thoughts:

1. Was there a "session zero" in which the group's expectations for the campaign and interactions were laid out? If not, it may be a good idea to pause and have this. Sometimes groups who are familiar with each other skip this because they "know each other", but it can still be good on a campaign-by-campaign basis.

2. When you discuss it with them, try to start by determining why the DM is acting this way: Since it sounds like the DM likes firmly heroic characters, is this just what they find 'cool' or do they actually object to playing / having grey-er characters in their party or campaign? (Same kind of applies to the cleric's player - are they just "playing the character", or is this what the player feels is right?)

3. Ask if there's been any miscommunications involved. The thing that sticks out as odd to me here, is that the DM clearly seemed to be urging you towards combat with stereotypically evil enemies in these scenarios... but views you initiating combat as "evil"? It's possible something is getting lost in translation.

4. Since you and the rogue are both clearly enjoying less cut-and-dry characters, express that this isn't just you-versus-them. Or you-versus-cleric-player. Broadly, try to avoid turning this into an argument between people.

5. This will fluctuate a bit depending on how roleplay-heavy your group is, but consider asking if this could be dealt with in-character. Is the cleric open to having a crisis of faith over working with such "tainted" people? Are you okay with your character sometimes being held back by other party members when they'd like to be proactive, so long as their view isn't changed?