Negotiating always has a risk. The risk that an offer might get retracted. With that said, most employers are unlikely to retract an offer just based on you attempting to negotiate the compensation package. Generally, the higher the position, the more room you have to negotiate.

Some positions have fairly fixed pay. Larger law firms often have fixed pay scales based on your years of working as an associate. There is often very limited room to negotiate. While a legal assistant position might have a bit more flexibility, in larger firms your ability to negotiate might be limited. In smaller firms, this is not always true.

If you are looking at a legal assistant position with something other than a large law firm (smaller firm or legal position in a different type of company), negotiating will likely be more effective. If it is a large firm, your recruiter might be right. I have not looked into pay scales for support staff, but I know my pay is very rigid and negotiating for pay won't get me anywhere.

Source: Fourth year associate at a top 50 law firm .