"Islamic terrorism" in its current context is motivated by a wish to impose a particular form of Islam on others. It is aimed at beliefs rather than actions, and is aimed at other views of Islam as well as believers in other religions or in none. It is a journalistic shorthand which serves to condense a complex issue into a few words.

That seems to me to be very different from an attack on an abortion clinic, which is motivated by the perpetrator's views on abortion. These are probably likely to be derived from a religious point of view, but I think it would be misleading to call this "{insert religion of choice] terrorism". In the current context, it is something quite different, even if religion may be part of it.