We've been dosing people with hydroxychloroquine for malaria for years so it would be very surprising if it suddenly turned dangerous. It's pretty clear at this point from a number of randomized trials that giving it to people who have developed Covid-19 isn't particularly useful. It's still possible that it might be useful prophylacticly, there's been some promising non-RCT studies coming out of India and at least one RCT underway, but I'm not sure I'd bet on it.
EDIT: And to be clear the Indian studies suggested you wanted to be taking it for weeks before first exposure to SARS-2.
Just because something is a useful medicine that's been given for a while doesn't mean it can't also have serious side effects, some of which could conceivably exacerbate Sars-CoV-2.
Or not, there's no evidence that it does. But a lot of medicines are "dangerous", including Plaquenil, particularly if applied for the wrong circumstance or given to people with contraindications.
EDIT: And to be clear the Indian studies suggested you wanted to be taking it for weeks before first exposure to SARS-2.