I mean like, he can't legally nor physically stop you from going to London. It may cause a slight rift in the relationship with him, but you'll have to deal with that when it happens. He'll have to get over it eventually, and I think it's better you have a minor falling out with him than regret where you study for the next 4/5 years.
Honestly, I don't think the crime rates of bath and London are THAT different. Maybe look at the different crime rates, and show him those. While London does have a fairly high crime rate, the rest of the UK does as well tbh. Most crime that happens in London is theft - just don't walk around with your phone out and it'll be fine. I've lived in London my whole life, and I attended a college near UCL during A levels and apart from a bike accessory being stolen 🗿 (outside my college, near UCL) I've had no other issues in that area. Within my local area - the only crime I've experienced was my bike being stolen from my garden because I didn't lock it up ;(.
London is a fairly busy place, and has areas that are quite deprived so will inevitably suffer from crime but it really isn't that deep. Apart from the phone snatchers, I do feel fairly safe in London. The UCL campus, and surrounding areas are also always incredibly busy so apart from potential pickpocketing and phone theft, I highly doubt you'll experience any violent crime etc.
People from across the globe travel to London to study at UCL, and they make it out alive so I'm sure you'll live. I think that London crime is often sensationalized and made out to be worse than it actually is, but it really isn't so bad here and I honestly regret not applying to UCL for Psychology because I initially didn't want to stay in London but I have fallen back in love with my home city (I'll be attending York, instead, so quite different to London).
I did also apply for Bath, and while the city is very very nice, it is also extremely busy (on the day I went anyway) and small.
Also, I'm not sure what gender you are, but I have experienced sexual harassment here - so I'm not sure if your dad is worried about that (if you're a girl) so that MIGHT be something to look out for, but honestly women experience that across the UK so it isn't limited to London.
That's really the only bit of advice I can give - my own mother is weary of me leaving London and being so far away, but I don't think she's as worried as your dad is so she hasn't done much to try and convince me not to leave.
perhaps take a look at this article which outlines the different levels, and types of crime across unis:
https://www.thecompleteuniversityguide.co.uk/student-advice/where-to-study/crime-rates-in-university-cities-and-towns