Lots of crawlers do this. I have never seen a webserver that does not get a variety of these from obviously different sources. Even just an ssh port will get a lot of malicious login attempts.
I am not saying its OK. I am saying it is probably not this crawler that is hammering your site, and definitely not only this crawler. I specifically mentioned malicious attempts at ssh logins.
No - scanning without consent is abuse and anyone doing this is malicious regardless of what they tell themselves or anyone else.