Frankfurt am Main — Bayer CEO Werner Baumann was on the defensive at the German chemical giant’s AGM on Friday, relitigating the decision to buy US seeds and pesticides maker Monsanto before restive shareholders.

About 500 protesters gathered outside the Bonn conference centre with placards mocking Bayer’s corporate motto “science for a better life” or calling to “stop glyphosate”, the Monsanto-made herbicide at the centre of the group’s woes.

And supervisory board chair Werner Wenning said in his introduction that “a string of shareholders have asked if the Monsanto buyout was the right thing to do”.

Some 13,400 US lawsuits relating to glyphosate and initial unfavourable judgments against Bayer “are placing a heavy burden on our company and worrying many people”, Baumann acknowledged in the first moments of his speech.

Bayer’s share price fell by about 40% following its $63bn takeover of Monsanto last June. The plunge was driven by the first of two jury rulings so far that have awarded plaintiffs —  glyphosate users diagnosed with cancer — $80m each.

Baumann complained that such decisions have been based on a 2015 finding by World Health Organisation’s International Agency for Research on Cancer (IARC) that glyphosate “probably” causes cancer.

“We remain convinced of the safety of glyphosate,” the CEO said, recalling that the IARC judgment had prompted regulators worldwide to re-examine the chemical. Baumann cited Health Canada, which, in January, said it had “left no stone unturned” in a review but found no new evidence that the pesticide causes cancer.

In the two cases already heard, “we remain optimistic that the next higher courts will reach different verdicts”, the CEO added, calling for “decisions based on scientific analysis — and not on emotions”.

The business case for the merger remains as strong as ever, he assured investors, with the merged companies now operating “leading businesses in chemical and biological crop protection, in conventional and biotech seed, and also in digital farming”.

And he reiterated the group’s targets — including its pharmaceutical and over-the-counter medicines units — to increase sales 4% to €46bn in 2019, with an operating profit before special items of €12.2bn.

Current market reactions were “exaggerated” and did not reflect Bayer’s “true value”, he said.

Baumann’s sticking to his guns did not enthuse Frankfurt investors, but caused no further stock market upsets, with the group’s shares down 0.1% at €60.96 at about 10am GMT against a DAX 30 index of blue-chip shares up 0.1%.