Anne Bryant is quoted in OnBecomingaLeader (p.127) as saying "Too often you come into a new job with a wave of fresh energy and, not by design, you tend to debunk what's been previously done. That's very hard on the people who've been with the organization for a while [see HumanInteractions]. It's better to try to put yourself in their shoes and acknowledge the good things that have been done and reinforce those things, before going forward with your own plans."
OTOH, if what they have is bunk, you might be doing most of the people in the organisation a favour by de-ing some of it. Anyway, why did they hire you if not because there's something wrong or lacking with what they have now?
Yabbut, if you jump right in and immediately start de-bunking you might doom your relationships with the incumbents. People can be sensitive. I think the point is that jumping into a new context and immediately alienating everyone there is something of a cultural anti-pattern. You might first try to build relationships with people before trying to influence their opinions. And it still might not work. Yeah, I know, it takes time, and the business might not have time. But I guess that begs the question of what are the cultural values of the organization (see CultureIsTheManifestationOfLeadership).
Having done this I agree with the caution. On more than one occation I have gone into a project, said "Why would we do it that way? ... We need to do this..." and found out later that there were very good reasons behind the decisions, even if I don't agree with them. The point is, yes I have been brought in to bring value, but it is too easy to gloss over less understood aspects of the project and decide the first design was bad. I think most of us think we are right, otherwise why do it? -- RickSperko