It's not that professionalism is bad, it's that nobody knows what that even means anymore. People now use it mostly to attack other people by saying that are "not professional".

I don't always agree that you need to make the client comfortable. They often have big problems which can be socially painful to fix, especially when they don't have the experience to know how to do it themselves (i.e. no dev machine, no sane testing process, and so on). They can feel threatened by someone who does know what they are doing, and they transfer that hostility to you. They fear change. It's just the way that some clients are.

When you think something needs to change, you need to find out why it's that way in the first place. There are probably some stakeholders in the group of people you are working with. Before you tell them how they should do it, find out why they decided to do it that way. Get names and history. This is really tough to do as a telecommuter since you don't have lunch or have other casual social situations where you're supposed to get this sort of information.

Once you have a better idea of the history, suggest small and easy changes, wait, and repeat. Your job is not to fix every problem right away. Feel satisfied if you can keep them moving in the right direction, even if it's not as fast as you would like.

You can't always give in to just get along either: you've probably been hired to fix things (not necessarily "shake things up" though). If you give in, you aren't doing what you were hired to do, and you have to figure out if you just want to do the job and get the paycheck or solve the problem.