Well, I do use fossil fuels in various ways (I have a car, I have a heated home, and I consume electricity which is approx. half fossil locally) - and yes, I do not consider continuing to do so unethical. It would be preferable to use less fossil fuels, which is a consideration for me, but I definitely do not consider that there's an ethical duty for me to use zero fossil fuels.

While we can (and should!) agitate for policy changes to reduce fossil fuel usage, it's appropriate to request that, I do not consider that it would be ethically appropriate for me or you to demand total "fossil abstinence" from any person around us - freedom and respecting others' freedom is also a valid ethical value, and actually imposing your will on others requires substantial justification, and having ethical ends do not imply all means would be ethical.