It's not a secular holiday at all. It's still very much completely about Jesus' birth. There is a difference between what atheists and non-Christians celebrate and what Christians celebrate.
Also, it was not around before Jesus. That's just not true at all. Otherwise, it would not be called Christmas. There may have been a Pagan festival before Jesus' birth, but that can't possibly be misinterpreted as the same thing as Christmas- they're clearly two different things.
And about the Royal Family. Firstly, you can't use the argument that they're foreigners, as, technically speaking, we are mostly made up of Vikings, Normans or Anglo-Saxons- none of which, you could suggest, are original British people (ie. the Celts).
About the Royal Family being homophobic, racist etc. I don't care. I don't even care about the Royal Family at all.