First, young mothers with small children (photo from @mama_jp):
The sign says, "Adults should protect the future of children. We're against disaster debris burning. Protect Kyushu for Japan."
Professor Yukio Hayakawa's tweet was: "Mothers in Kitakyushu, have they all gone nuts?"
On his May 23 blog, he proclaimed, "This day will be long recorded as the day when the discrimination against Tohoku has started."
He probably has not seen this picture of Kitakyushu City officials blocking the passage (photo from @Saikeman):
If he did, he may highly approve of the high-handed way the Kitakyushu City officials have treated the whole issue - from not bothering to tell anyone (residents, neighboring cities) to laughing at the protesters to calling the police to disperse the protesters yesterday. The professor is recommending that Kitakyushu City declare independence from the rest of Japan if the residents want to keep out the disaster debris.
The city is test-burning the debris from Ishinomaki City, Miyagi Prefecture right now at an incineration plant for regular household garbage. In the test burn, 1 part of disaster debris is supposed to be mixed with 9 parts of household garbage and burned. Protests apparently have no impact to the city officials or the mayor, and the residents of Kitakyushu City are indifferent for the most part, I hear.
NHK reports that about 70 people are protesting near the incineration plant, but there are more than 150 policemen blocking the road to protect the debris-carrying trucks.
Kyushu have been mostly spared from the fallout from the Fukushima accident, so the residents' sensitivity to radiation contamination is probably not the same as that in Kanto or Tohoku. Professor Hayakawa's later tweet says "176 becquerels per kilo? That's just normal."
Measurement of soil for cesium-137 in the nearby Fukuoka City in 2010 was 2.3 becquerels/kg. The highest I could find was 155 becquerels/kg in 1964. (Data from Japan Chemical Analysis Center)
Radioactivity of disaster debris from Ishinomaki City, Miyagi, from the Ministry of the Environment: