A particular accent may require you personally to listen more intently but there is no such thing as an intrinsically "difficult" accent
Of course there is
How the frig do you think people in Glasgow communicate with each other
I don’t know where to begin with this. They are attuned to their own accents so of course they understand each other.
Yes, it’s terrible how some people’s lives can be affected by the prejudices they had as children
A person with a “strong foreign European accent” is not “a poor communicator.”
It’s not prejudice. When you are having a one to one conversation with someone with a strong accent you can ask them to repeat themselves. You can’t ask a teacher or university lecturer to repeat themselves all the time. They might be a brilliant communicator and explain things well, but if it is in a difficult to understand accent then students will struggle.
Those posts about lecturers were disgusting. I hope that none of that happened.
Bangs head against a brick wall 
If you can’t understand the lecturer it is a massive problem for the students. They can’t stop the lecture and ask the lecturer to repeat themselves. It is harder for STEM subjects when there is a lot of new vocabulary to learn, and makes it difficult to google search when following up a lecture when the word they have written down bears no resemblance to what it should sound like.
Having a difficult to understand accent doesn't seem to stop companies outsourcing their call centres to off shore teams
A lot of them have been brought back to the UK now because they received too many complaints @Justkeeppedaling. I can’t remember the last time I spoke to someone with an Indian accent at a call centre.