My boyfriend is Dutch, and he says: when you are talking TO someone you say TEGEN, and it means TO (never against). You are saying something TO someone. There is a slight difference when you speak MET someone, and it implies both sides communication: Ik spreek met Tom. Same thing in English with "speak to and speak with" You can say "Ik ben TEGEN jou", and it means I am against you, but with "spreken" TEGEN means TO
Hij spreekt zich uit tegen hen.
Zich is needed in this sentence, because uitspreken is a reflexive verb (zich uitspreken). Next to that uitspreken is also a separable prefix verb, uit moves to a different part of the sentence, but is really an essential part of the verb.
- I speak (out) against them translates as Ik spreek me uit tegen hen.
- We speak (out) against them translates as Wij spreken ons uit tegen hen.
Your assumption makes sense but makes an otherwise simple language suddenly much more difficult.
As Andy.Linde pointed out above, this sentence is "Hij spreekt tegen hen", translated by DL as "He speaks TO them" whereas the previous sentence was "Ik spreek tegen haar", translated by DL as "I speak AGAINST her."
So, because the elements of each of these sentences are (elements...are) the same, the translation of "spreken...tegen" should be the same.
The original meaning of against and tegen is opposition, but like most frequently used prepositions they have acquired generalised meanings. E.g. in English, you can lean 'against' your girlfriend/boyfriend without any negative connotations. It's just an accident of language history that you can't also speak 'against' someone in the sense of speaking towards them.
Your explanation is very much like the meaning of 'prevent'. Contemporary use, of course, is to mean 'to stop s.o. or s.th. from happening before it begins'. Prior usage of 'prevent', meaning "pre-venture" was 'to go (venture) before'.
Nevertheless, your explanation does not answer the basic question here regarding the use of 'tegen', which really should be as someone stated above: Why does "spreken...tegen" mean "speak to(ward)" in this sentence but "speak against" in a previous sentence of the same grammatical structure?
I will ask again since no one has mentioned it in a year and it doesn't seem any of the people asking the question really ever got an answer. Why is 'He speaks against them' not accepted, when in a previous exercise, 'Ik spreek tegen haar' was translated as 'I speak against her'? I understand that 'tegen' can mean both to and against, so it seems that both 'he is speaking to them' and 'he is speaking against them' should be accepted. Please help. This prepositions section has my head ready to explode.
As a native German speaker who is still just learning Dutch, I can only guess. Here is some background information that may help to understand what's going on.
The database of accepted answers for a question is often incomplete, especially when it concerns rarely given answers or answers that have many variants which Duolingo's algorithm does not recognise as equivalent. It also often contains incorrect or misleading answers that are accepted as correct because someone once reported them as such and they were accepted in error.
The Dutch third person plural object case pronoun is special in that it's the only one for which it is still possible to distinguish dative and accusative, the original cases which were merged into the unified object case. As far as I know it is legitimate not to make a distinction since it had already been lost almost completely and was only re-introduced later. But a lot of people insist on the distinction, in which case they use hun for datives (indirect objects) and hen for accusatives (direct objects).
There is a separable verb tegenspreken = contradict, speak against which ordinarily seems to take the accusative (though the German cognate takes the dative, and so this may have been more correct in Dutch as well, some time ago). But we can also just use the simple verb spreken with the preposition tegen, which also takes the accusative. So there are two ways to form the sentence "Hij spreekt tegen hen":
- Hij spreekt tegen hen. - He contradicts them. (Formed using tegenspreken - though this is rather questionable, as the normal way to use a separable verb would result in "Hij tegenspreekt hen".)
- Hij spreekt tegen hen. - He speaks towards/against them. (Formed using spreken + tegen)
I can form several hypotheses for what's going on from this data, but unfortunately I don't know which of them, if any, is correct. There are also other possible explanations, e.g. that the sense "speak against" may have fallen out of use, but so recently that native speaker can't agree whether to still consider it a correct alternative.
Anyway, I think the best option is to remember that "spreek tegen" is well established (somewhat surprisingly) as a way of saying "speak to/with", and that consequently it's better to avoid "tegenspreken" due to the potential for confusion. There are unambiguous alternatives such as weerspreken.