Depending on where you live, some LPN programs are just as competitive as RN programs, especially if the same school offers the bridging to RN.
However, this all depends on a few things-if you were an LPN that graduated from a vocational school, your credits would not transfer into an RN program, because you would be learning college level anatomy and physiology, chemistry, microbiology, english and psychology. Taking those pre-requisites and co-requisites alone may take at least a year. Many programs do offer advanced standing once the pre-requisites are completed for LPNs by dropping the first semester.
I think that the advisor was saying that because you did not drop the classes the proper way, that those grades (probably were F) were computed into your GPA, making it drop considerably, which would make you less competitive. However, most schools would not count classes that are not pre-requisites into their RN programs as part of the GPA, and since you are saying that these classes were going towards Liberal Arts, it seems that you may not have taken the core courses I mentioned earlier.
I know you are annoyed with them; but in the future, make sure that you know the policies of the schools regarding dropping courses, late registration, the required GPA for application into nursing programs and whatever so that you don't face this again.