You could implement this pretty easy in a Web Forms flow.
Use a Get HTTP Request Value component and specify USER_AGENT as the variable to get. This component fetches the user agent string of the machine making a web request, and it exposes a lot of different things like browser, browser version, etc.
Once you have this, you can parse it to determine what browser is being used (MSIE = IE; Mozilla = Firefox). You can use an Index of Text Within Text component to do the parsing... if the index of "MSIE" is zero or greater, then the user is using IE.
If they have a bad browser, you can then direct them to a "bad browser" form.