It depends on how the stainless (in fact any material) fastener is used. The above picture shows shows the galvanic corrosion of an aluminum plate (after just six months) caused by using a stainless steel screw. The stainless itself doesn’t corrode, it causes the aluminum to corrode.
In the above situation if you used a cadmium-plated steel screw (like Ducati stock hardware) the cadmium plating would corrode first, and in doing so, protect the aluminum part instead of the other way around.
In fact, that’s what you’re seeing when you’re looking to replace that scruffy-looking hardware ... the inexpensive fastener’s plating protecting the expensive aluminum and magnesium parts.
So, what I’m warning here is that if you replace your corroded fasteners with a corrosion-resistant (but more-dissimilar) material such as titanium or stainless steel, you can shift the corrosion to the aluminum or magnesium if the two dissimilar metals are touching. Anti-seize materials will help by inserting a third material that itself will corrode and thereby slow down the galvanic action.