No, you’re protected based on things like sex, gender, and race. That means it’s just as illegal to fire you for being straight, white, cis man as if you’re a lesbian black trans woman.

It would help if you mentioned what country you are talking about as LGBTQ+ people are not protected worldwide.

No, nobody can be fired for whatever gender, sexual orientation, religion or beliefs they have. The focus on LGBTQ+ or certain religious beliefs is due to the media focus and because of the countless instances where such terminations, both legal or illegally, have taken place. These legislations give these groups the same rights everybody else already enjoys, and are usually formulated in such a way that any discrimination in regards to gender, etc. are forbidden, this includes white, straight cis-men.

As others have said, it depends where you live. For US states that prohibit discrimination on the basis of sexual orientation or gender identity, it protects heterosexual and cis people the same as gay or trans.

https://en.wikipedia.org/wiki/LGBT_employment_discrimination_in_the_United_States

In EU no, you cannot be fired because you’re straight. Not sure how the law is in other parts of the world.

Persecution complex much?

LGBTQ+ and labour laws are very different across countries, so it’s very difficult to talk generally about how this works without being specific to some country.

I will talk about Spain because there’s where I am from and where I worked most of the time.
You generally just cannot fire someone for arbitrary reasons before their contract comes to an end. You really have to justify why you need to fire that person, like having several poor performance reviews against them. Otherwise, you may risk having your firing judged as “unjustified” and having to pay that person a big compensation or even the firing being judged as void and having to readmit them to the position you fired them from.
No matter whether they are cis, gay, straight, man, woman, POC or whatever, you just cannot fire someone without a valid reason unless their contract has come to an end and you don’t renew it, that’s basically it.

So could someone argue that your sexual orientation or gender identity is a valid reason to fire you because being gay doesn’t fit within their company culture or having trans people may cause them an image problem?

No, article 4.2.c of the Worker’s Statute says you cannot be discrimanted for employment based on sexual orientation or gender identity, among other criteria like ethnicity, age, union membership, etc.
So you couldn’t be fired for being either gay or straight, man or woman, cis or trans, etc. Nothing of that is a valid reason to be fired.

No. It quite literally means that you also cannot be discriminated against for that. In fact, the protections that make it illegal to discriminate against LGBTQ+ individuals are the exact same protections that prevent discrimination because of your being straight, and if you were to repeal the former, the latter would be lost as well.

You have it, quite literally, entirely backwards.

Not that I know of. Never heard of anything like that.

No, because that’s never been a thing and thus straight people require no legal protection, whereas LGBTQ+ people have often found themselves fired solely on the basis of their sexuality, therefore they need legal protection.

I want to know where in the world you are that LGBTQ+ is specifically protected, rather than rather than the protections being applied to sexuality and gender as a whole? In other words, do you know what you are talking about?