That's an ethical question rather than a legal one. It is however the owner's responsibility if someone is hurt either on razor wire or elsewhere on the property as property owners have a duty of care to anyone on their property - even those un-invited guests!

However, if it's surrounded by a six foot fence (or locked doors) and you have to break something to get in, the law of 'Breaking and Entering' comes into play which is separate from trespass.