Promoting competitors through affiliate links

It feels like what I'm about to ask is really silly, but I thought it's worth asking before I make a mess of things

If I run a site based on "apple pie" for example, is it okay for me to compare multiple sites selling "apple pies" (price/quality/postage etc.) and have affiliate links to all of them? I ask because many affiliate sites I have looked at have said if they don't like the other content of your site then they reserve the right to remove you from the program which is, of course, understandable, since you may be giving their rivals more trade.

I would just like to know if this is a "set in stone" rule which will get me insta-banned from any/all affiliate programs if I do it. If not - how likely is it that I will be removed from the program?

Sorry for the silly question! Thanks in advance.

It's not only okay, it's a great idea. If you've ever seen any of the truly professional, high-traffic, business-grade websites which promote affiliate offers, many of them promote multiple "competing" products. The idea is to play off of the individual products' strengths and functions, and to explain how they differ from one another and how they can individually help the end-user achieve their goals.