How one might formalize normative statements such as your quote?
Any statement "X should Y" carries an
implicit " .... if X wants Z" with it.
Whether someone says it or not, it is there -- even if only in the head of the person who made the statement.
So for me to say "you should be very suspicious of people who are so obsessed with objective 'good'" is really saying " you should be very suspicious of people who are so obsessed with objective 'good'
if you care about people disclosing their true intentions with you, and I assume you do," etc.
Already, we are well on the road to complete formalization. In the expanded context, such as that above, "you should" clearly means something like "the behavior with the highest probability of resulting in reaching your goal, all else being equal, in my opinion, is to ..."
So now we have :
"the behavior with the highest probability of resulting in reaching your goal, all else being equal, in my opinion, is to be very suspicious of people who are so obsessed with objective 'good'
if you care about people disclosing their true intentions with you, and I assume you do"
Just to get you further along, I will formalize some of the other terms in there.
"in my opinion" can be formalized to "according to the conclusions reached by logical inference I have performed, possibly subconsciously, and/or insight I have had, the source of which is still not agreed upon by human philosophers/scientists .. ... because such people are often motivated by motives that are not immediately apparent..."
"if you care about" can be formalized to "if it would benefit you somehow, even in a purely psychological manner, for .. to ..."
So now we have:
"the behavior with the highest probability of resulting in reaching your goal, all else being equal, according to the conclusions reached by logical inference I have performed, possibly subconsciously, and/or insight I have had, the source of which is still not agreed upon by human philosophers/scientists, is to be very suspicious of people who are so obsessed with objective 'good' if it would benefit you somehow, even in a purely psychological manner, for people to disclose their true intentions with you, and I assume you do, because such people are often motivated by motives that are not immediately apparent"
Should I go on?
I never said it would be short and sweet. But it can be done.