You will notice that once a TB sufferer is identified, the proper procedure is to trace all contacts for testing/treatment
The proper procedure is NOT to place said sufferer on hideously over crowded barge with 499 other vulnerable people.
a bit of legionnaires in the pipes is not a big deal
SERIOUSLY! Legionnaires is deadly, you get that right. It kills at least 10% of everyone infected.
Yes, these disease occur, as you say, but they are deadly, and they are dealt with accordingly, with isolation, tracking, treatment, testing, control, as you have outlined.
What does not happen is deliberately introducing them to hideously overcrowded refugee populations, which appears to be what has happened here.
If, on your plane, the rather than being accidently exposed, the individual was identified as contagious with TB, THEN brought onto your plane and sat next to you, that would be different, wouldn't it.
If in your house, legionnaire's was discovered, then you and your family were forcibly moved in without any steps taken to eradicate it, that would be different, wouldn't it.
You have exactly proved my point. These are deadly diseases. There are appropriate reactions to them, as you have described. There are criminally irresponsible reactions to them, which is what has happened in the case of this barge.