I my experience, at least for an individual, I think saying no is exactly the opposite of dangerous. I’ve been contracting exclusively for 10 years and said yes about 6 times and no dozens or hundreds of times. As long as you say no frankly, with a reason, and offer some names of people who can help, people are happy with you and will more often than not ask again in the future. Saying no, especially for bad fit, is one of the most important parts of success I’ve had in consulting.