Although bad language would appear to have a wide meaning, I think in the context you mention it would be clear that it would refer to swearing and the like; foul language would also be another viable option.

I am fairly sure that the phrase is more or less literal.

It simply means 'excessive language'. Please see the definitions below.

Perhaps!

Profanity also known as swearing, cursing, foul speech, and cussing, is a show of disrespect, a desecration or debasement of someone or something, or just the act of expressing intense emotions. Profanity can take the form of words, expressions, gestures, or other social behaviors that are socially constructed or interpreted as insulting, rude, vulgar, obscene, obnoxious, foul, desecrating or other forms.[1]
http://en.wikipedia.org/wiki/Profanity

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Note added at 15 mins (2012-02-02 01:16:15 GMT)
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I stick by my original answer but offer these references in case you feel they better fit your context:

Periphrasis
Definition:
The term ‘periphrasis’ refers to the use of **excessive language** and surplus words to convey a meaning that could otherwise be conveyed with fewer words and in more direct a manner. The use of this literary device can be to embellish a sentence, to create a grander effect, to beat around the bush and to draw attention away from the crux of the message being conveyed.
Example:
Instead of simply saying “I am displeased with your behavior”, one can say, “the manner in which you have conducted yourself in my presence of late has caused me to feel uncomfortable and has resulted in my feeling disgruntled and disappointed with you”.
Gossip and Nonsense: Excessive Language in Renaissance France

Dr Emily Butterworth is Co-Investigator on this AHRC-funded project, which will examine the more demotic and marginal aspects of Renaissance copiousness. She is collaborating with Dr Hugh Roberts (Exeter), and will work on the strand on gossip and its uses and representations in literature.
http://www.kcl.ac.uk/artshums/ahri/projects/gossip.aspx

non•sense
n.
1. Words or signs having no intelligible meaning: a message that was nonsense until decoded.
2. Subject matter, behavior, or language that is foolish or absurd.
3. Extravagant foolishness or frivolity: a clown's exuberant nonsense.
4. Matter of little or no importance or usefulness: a chatty letter full of gossip and nonsense.
5. Insolent talk or behavior; impudence: wouldn't take any nonsense from the children.
http://www.thefreedictionary.com/nonsense

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Note added at 2 hrs (2012-02-02 03:37:27 GMT)
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AS AN AFTER THOUGHT, all the above related terms, 'excessive language' and 'profanities'/'foul language', are right, so it depends on what you reckon from your text and if there were any doubt that it's not referring to the unionists' liking for a good cuss-word, then if you say 'excessive language', although it may be vaguer, it's also broader; broad enough to include gossip, nonsense, surplus and unnecessary words and, of course %#&(´¿{.-{+* :)

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1 Jan 2012 – Refrain from excess foul language. 8. No stealing. 9. Cut all of the tree down when gathering logs. Replace cut trees with saplings (we value an ...


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Note added at 6 hrs (2012-02-02 07:40:12 GMT)
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eski :))

in wide sense, generally keeping one's language nice and not likely to cause offence

Another option

a possibility

another option that comes to mind