With all due respect, your opinion of Montessori is based on a very isolated experience, and also seems to be a rather misinformed one as well. As a certified Montessori educator at the primary (preschool) level, I can tell you it is certainly not due to Montessori's teachings or beliefs that a child would be ostracized EVER, or excluded or singled out in any way.
As for the teachers being snotty, that certainly sounds like something unique to their individual personalities, and not necessarily present in all Montessori educators.
To say that Montessori is touchy feely is grossly inaccurate. And after having taught in traditional preschool settings for nearly a decade before switching to Montessori, I can tell you there is more structure and order in that environment than in any preschool or traditionally taught classroom. The only difference is that the discipline and structure is not tyrannically imposed by the teacher, yet there is a modeling of respect, conflict resolution in a pro-social way, and fun...yes, dare I say FUN in a Montessori environment. That being said, there is the expectation to adhere to ground rules and complete the work cycle fully. This is meant to increase the sense of order, concentration, coordination and independence that are so crucial to success in a more traditional setting (i.e. children expected to sit at a desk).
To say that Montessori is void of structure and routine is simply ignorant. Montessori is based on the premise of repetition and honoring the child's sensitive periods of development. You talk of children being expected to "accomplish" learning tasks. In a true Montessori environment, the children are not expected to accomplish tasks without first having a one on one or small group lesson.
As for not allowing you to drop in, our Montessori school has an open door policy, as should any preschool. If they don't, it is perhaps best to seek another environment. That is not Montessori's way, so it is unfair to attribute that one school's policy to Montessori. It sounds like you had a bad experience with a preschool who is misrepresenting the Montessori name/philosophy. Please do everyone a service by refraining from applying those bad traits isolated to that school to Montessori in general. That is merely close-minded, and serves to perpetuate misunderstanding and intolerance.