How do I discuss my fetishes with wife when she is very sexually passive and insecure?

Lots of reassurance! Starting small. If she is insecure - is there anything you (or the two of you) can do to help her feel more secure? Is there anything she does like or want that helps her feel less passive. Is her passivity a result of her insecurities - maybe exploring together would help? Lots of good information - there are good books and websites that will help. That would be a start. 

It might be easier to start bringing up fetishes then - with an understanding that we are all wired differently when it comes to sex, and some people are more kink or fetish oriented. It could be a vulnerable conversation, but one worth having. Find some good educational websites that talk about your fetish without judgement.

Start with something you think she'll be most ok with, something she can easily learn about and gain some confidence. See her reaction.  Reassure her. Explain to her what it means to you and what it would give you. Risk being vulnerable. Connect with her, truly. Be very patient. Set her up for success. No pressure, no judgment. See if you could present it in a way of exploration, discovery, creativity, play. 

A good counsellor will help with that conversation and exploration. 

Do  you know whether the reason your wife is sexually passive and insecure is due to your fetishes?

Maybe she'd be very turned on by your fetishes.

Try to not mix up your hesitancy to speak about your fetishes which she hasn't yet directly heard from you, with your assumption that her sexual passivity necessarily means she will reject or withdraw from you when you speak of your fetishes to her.

   Thank you for asking your question. When I read terms like "fetishes" and that your wife is "sexually passive and insecure" I can't help but wonder that there may be more going on within the coupleship and with yourself than what has been asked about in your particular question. 

   I invite you to enter into an exploratory journey with an experienced therapist to identify your fetishes and the deeper story behind the "who", "what", "when" "where", "how" and "why" they are important to you. Additionally, consider whether or not you need these fetishes as a requirement or strongly preferred for sexual excitement; and in its absence do you find yourself being sexually avoidant with your spouse or suffering from some form of erectile dysfunction. 

   While the fetishes may not be causing you clinically significant distress or impairment in functioning it seems from your question that they might (or would) cause distress to your wife. An experienced clinician could help you and your wife to navigate through this relational terrain ensuring all are heard and that the coupleship is honored. Best wishes.