I think they put him the `dance off` so that they could vote off Natilie and Vincent because of his poorer first attempt, knowing that in the dance off he would do it better.
As you say, it was 'alleged'. He's not been charged or tried and certainly not found guilty (at least, not by the law), so there's no reason for them to 'sack' him.
It was a photographer who alleged the assault and he refused treatment from medics at the scene but went to hospital afterwards for treatment. I am not a fan of Ricky Whittle and dont want him to win strictly but you could read between the lines here and come up with a few different stories - so I suppose innocent till proven guilty
And the photographer in question also accused Paul Gascoigne of assault a few years ago but later dropped the charges. This is either a very unlucky photographer or, more likely, one who deliberately provokes situations.
Ricky is not a big-headed thug and I think it is a shame if people didn't support him because of this incident.