These are explicit acts, not thoughts, and not new offences.
"Contempt of public official", I think they mean "outrage a agent" in French, does not mean the feeling but the act of showing 'contempt' as in insulting or threatening.
For example, if you take part in a demonstration and you insult a police officer for whatever reason they can arrest you for "contempt of public official".
"Participation in a group with a view to committing violent acts", which is not an offence specific to France, allows the police to arrest and charge people before they commit violent acts when it is clear through their actions that this is what they are planning. In relation to public demonstrations this may mean a group of people showing up with helmet, shield, or legal 'weapons' (e.g. slingshot and steel beads, or what not).
Likewise for the ban on face coverings, it is primarily to deal with people showing up with bike helmets, gas masks, etc. in order to (a) protect themselves against tear gas, and (b) not be identified (usually while they commit violence against police and property).
> "“It is ironic that a country with such a long and proud tradition of collective action for social change is criminalizing protest in this way"
On the contrary, it's because France has a long tradition of 'collective action' (i.e. really riots and revolutions) that a body of laws to counter violence has come about.
> The French authorities must stop criminalizing people and amend all the laws that hamper the right to peaceful assembly.
The offences mentioned above are not related to peaceful assembly.
Amnesty International is being rather disingenuous in this article.