You can choose whatever criteria you like for the candidate you support in the primaries, just bear in mind that some people are different from you, their priorities might be different, and that doesn’t necessarily make them sheep.
Bernie Sanders has probably engaged less in triangulation than any major American politician in my lifetime. That is a thing of wonder. However, ideological purity is not always the shortest route to effective change. As Saul Alinisky told us,
If you start with nothing, demand 100 percent, then compromise for 30 percent, you’re 30 percent ahead.