You just need to remove the “Index” from the group without clicking the node so that it never matches. Basically, you have 2 nodes with the same route signature here:
= "Admin"
= ""
= "Index"
, SiteMap, . , "" ( , , node, ), , .
<mvcSiteMapNode title="Home" controller="Home" action="Index" visibility="MenuHelper,!*">
<mvcSiteMapNode title="Customers" controller="Customer" area="Admin" clickable="false" description="Todos os clientes cadastrados" cssClass="icon-group">
<mvcSiteMapNode title="List" action="Index" description="Todos os clientes cadastrados"/>
<mvcSiteMapNode title="the customers" action="Details" preservedRouteParameters="customerId" visibility="SiteMapPathHelper,!*"/>
<mvcSiteMapNode title="New" action="New" />
</mvcSiteMapNode>
</mvcSiteMapNode>