It's not sensitivities, it's unnecessary thoughtlessness. There is a marked difference between people of one nationality making jokes about their own language to another of the same nationality and, although I am not a Welsh speaker ( can only just about manage my own!), I am sure they do exactly the same, but a huge effort is made in Wales to make every sign, everywhere, bi-lingual in order to help the much appreciated visitors feel 'at home'.
It is not only teachers who need to speak Welsh, it is many professions, including doctors. They are not excluded but are expected to take advantage of the many 'free' Welsh languages on offer to them and to reach a good spoken standard. I do not see this as discrimination in any way. When you think about it, it makes sense that you are able to speak the language of the country you want to work in, especially when there are many, especially older, people who do not speak English with any fluency! I am sure you would be expected to speak the language of the children you are going to teach in any country! When it comes to schools, it is not that it is compulsory to attend Welsh lessons, the whole school is taught in the language of the country - Welsh Medium Schools. For parents who do want English to be the language of teaching, there are some English Medium Schools and Welsh is taught as a second language in the same way that may English schools teach a 'foreign' language but the interesting thing is that it is the incoming English people who fight hard to get their English speaking children into the Welsh medium Schools!! I do believe that in England it is a requirement for English to be the language of necessity for many of the professions that come into contact with people. Even those people applying for naturalisation have to be reasonable proficient in English and to know something of British culture. We could discuss at length the problems of not being able to speak the language of your chosen country of residence to make a new life in!
Between ourselves, my husband and I used to have some laughs about the limitations of the Welsh language compared to our native language! It certainly wasn't joking or ridicule but simply the 'strangeness of the linguistic differences. eg. The Welsh use 'green' to describe many different colours including 'blue', all according to context - I could never understand this but then I am not Welsh speaking. Another is a 'ginger' cat is an 'orange' cat. I could go on at length … but I won't.
The one thing that still intrigues me is that, in conversation, both English and Welsh words are all used together!! It does have the advantage that I can usually get the gist of what they are talking about.
According to this roughly 30% and growing was the amount of post 3 yr old welsh speakers in Wales a coupla years ago, which is something to be very proud of.
https://gov.wales/welsh-language-data-annual-population-survey-july-2018-june-2019#:~:text=The highest numbers of Welsh,Isle of Anglesey (67%). But it does say that all Welsh speakers can speak English too, so I am surprised there are those who have to be addressed in Welsh by their doctor.
I went to senior (boarding) school in Gloucestershire but at least 1/3 of the boys were Welsh, so I came to really enjoy their company and sense of humour, I was also taught how to sing Welsh rugby songs such as "Sospan Fach" and of course "Guide me Oh, thy great Jehovah" especially on 1st March when the chapel roof was nearly lifted off. We all wore either a daffodil or a leek, and the leek wearers had to eat theirs before the end of the day. A mate ate his daffodil, for a laugh, he was then sick but went back into the dining hall to finish off his dinner. He was a Brit of Wiltshire farming stock.
This was 1968 -72 so of course the Welsh rugby team's star shone very bright, the "Pride of Lions" etc. Some of the Welsh lads spoke Welsh but by far the majority didn't. Although all my teachers had degrees from Oxbridge, many of them were Welsh. We had
three Mr Evans, one a French teacher, for example and two Mr Williams, one of whom taught me the trumpet. A Mr Parry, French again, the Head was a Mr Roberts. (French and German). Good linguists the Welsh it would appear!
When I was finishing my PGCE I was looking for jobs in the TES as of course you had to, pre computers, and the adverts for jobs in Wales were all written in Welsh which meant I had no chance of even understanding them, much less applying. Which was a shame as I would quite liked to have worked over the other side of the Severn.
Integrating into a country without being able to speak the language is a bit harder, it definitely helps and my wife finds it very hard as she is very dyslexic which got in the way of her learning it. She has spent more time in French classes than I did during my degree, she reads it reasonably well. Fortunately she tends to get mothered by our French friends as she tries her best and I translate for her when necessary. She bought a very expensive phone with a translator on it but our friends are a bit old to be able to use it with her easily.
So I have a big soft spot for the Welsh, in fact for all the Celtic peoples, including the Bretons!