I think the fear stems from the thought that the Dark Side is seductive. And while I have no doubt that for some it might be so, not every Jedi would find himself seduced by it. And I think Ani would have been better prepared to deal with Sidious had they thought of preparing him better.

Indeed. To be honest, I'm not sure why the Jedi thought the 'one size fits all' when it comes to the attachment rule. Some people need something or someone to keep the going. And I think by closing themselves in such way, they were very ill prepared to deal with Ani. And we all know how things go.